delivered the opinion of the court:
In Cole-Randazzo v. Ryan, 198 Ill. 2d 233 (2001), our court considered and rejected a challenge to the validity of the redistricting plan approved by the Illinois Legislative Redistricting Commission and filed with the Secretary of State following the federal decennial census conducted in the year 2000. During the pendency of Cole-Randazzo, 13 additional cases were filed challenging the same redistricting plan. Five of those cases were voluntarily dismissed by the plaintiffs shortly after they filed their briefs. The remaining eight cases are the subject of the proceedings before us today.
As with Cole-Randazzo, each of the eight new cases invokes this court’s original jurisdiction under article IY section 3, of the Illinois Constitution of 1970 (Ill. Const. 1970, art. IV § 3). Plaintiffs are various registered Illinois voters, some of whom are incumbent members of the Illinois General Assembly.1 Named as defendants are the Attorney General of Illinois; the Illinois State Board of Elections, the Board’s executive director and its members; and the Illinois Legislative Redistricting Commission (the Commission) and its members.
The actions were commenced when plaintiffs filed motions for leave to file their complaints in accordance with Supreme Court Rule 382 (155 Ill. 2d R. 382). We granted those motions, established a briefing schedule, and consolidated the actions for disposition. We also permitted John Tully, a registered voter, and Emil Jones, Jr., the Minority Leader of the Illinois Senate, to intervene as additional defendants. No oral argument was entertained.
All eight of the new cases were prepared by a related group of lawyers and seek the same relief: a declaration that certain of the representative (House) districts contained in the new redistricting plan are invalid and an order adopting, in their place, modified district boundaries as proposed by the plaintiffs. The cases differ only in the particular districts each attacks. Cause No. 92701 challenges the boundaries established by the Commission for Representative Districts 51, 52, 53, 54, 58, 59, 60, 61, 62, 63 and 64. Cause No. 92702 takes issue with the boundaries for the 99th and 100th Representative Districts. The 15th, 16th, 17th, 18th, 19th, 20th, 57th, 65th and 66th Representative Districts are the subject of cause No. 92703. Cause No. 92704 attacks the 75th, 79th and 86th Representative Districts, while the 50th, 83rd, 84th, and 96th Representative Districts are the subject of cause No. 92705. Cause No. 92706 seeks to invalidate the boundaries for Representative Districts 113, 114, 115, and 116. The 103rd, 104th, and 105th Representative Districts are contested in cause No. 92707. Cause No. 92708 pertains to the boundaries for Representative Districts 27, 28, 30, 31, 35, 36, 37 and 38.
Representative Districts 99 and 100 cover the area in and around Springfield. Representative Districts 103 through 105 include the City of Champaign and nearby areas. Representative Districts 113 through 116 are located in southern Illinois, including portions of the St. Louis metropolitan area. The 35 other districts are all situated in Cook County and the counties near Cook.
Some of the districts challenged in the foregoing actions, including Representative Districts 15, 18, 35, 36, 75, 99, 100, 113 and 114, were also singled out for scrutiny by the original and intervening plaintiffs in Cole-Randazzo v. Ryan, 198 Ill. 2d 233 (2001). The balance, though not specifically identified by the Cole-Randazzo plaintiffs, were implicated in that case to the extent that the plaintiffs there attacked the new redistricting plan as a whole.
The plaintiffs in the cases before us today make no claim that the process employed by the Commission in formulating the new redistricting plan was in any way improper. No procedural irregularities are cited. No assertion is made that the Commission failed to consider relevant evidence or took into account evidence it should not have considered. As in Cole-Randazzo, the sole issue is whether the particular districts challenged by plaintiffs comport with the compactness requirement set forth in our state’s constitution.
We undertake our consideration of plaintiffs’ claim mindful that under the Illinois Constitution of 1970, establishing boundaries for legislative and representative districts is a legislative function, not a judicial one. The duty to redistrict legislative and representative districts is expressly vested in the General Assembly. It does not become a judicial function merely because the members of the General Assembly are unwilling or unable to enact a new map within the time prescribed by law. When that occurs, as it did in the matter before us, establishing new district boundaries becomes the responsibility of the Commission, not this court. Ill. Const. 1970, art.IV § 3(b).
Where the Commission subsequently approves and files a redistricting plan, as it did here, the plan is presumed to be valid and must be given the force and effect of law. Ill. Const. 1970, art. IV § 3(b). In that respect, redistricting plans are directly analogous to statutory enactments, which are also cloaked with the presumption of validity. The presumption of validity means that courts must uphold a statute’s constitutionality whenever reasonably possible. Correspondingly, a party challenging the statute’s constitutionality bears the burden of clearly establishing the law’s constitutional infirmity. People v. Sanders, 182 Ill. 2d 524, 528-29 (1998). So it is with a duly approved and filed redistricting plan. The proponents of the redistricting plan before us today therefore have no obligation to prove to our court that the districts formulated under the plan pass constitutional muster. Rather, the burden is on plaintiffs, who are challenging the plan, to clearly establish that the map is not constitutional.
Where, as here, challengers to a redistricting plan allege that districts formulated by the Commission fail to meet our constitution’s compactness requirement, the applicable burden of proof requires those challengers to establish that the plan is against the manifest weight of the evidence. Cole-Randazzo, 198 Ill. 2d at 239. Under Illinois law, a decision is not against the manifest weight of the evidence unless the opposite conclusion is clearly evident. That other conclusions might be reasonable is of no consequence. If there is evidence to support the decision, it should not be disturbed. See, e.g., Abrahamson v. Illinois Department of Professional Regulation, 153 Ill. 2d 76, 88 (1992).
The redistricting plan before us today was the product of a series of meetings and public hearings held in September of 2001, following the selection of a ninth Commission member pursuant to the provisions of our state’s constitution. See Ill. Const. 1970, art. IV § 3(b).2 During those proceedings, the Commission considered various plans. It heard testimony and took other evidence regarding the plans’ strengths and weaknesses. Expert witnesses, community groups, and others were permitted to present their views. Among those whose voices were heard were the Mexican-American Legal Defense Fund, the African-American Working Group on Reapportionment (which included the Chicago Urban League and the NAACP), the Independent Voters of Illinois/Independent Precinct Organizations, the Midwest Community Conference, and the Asian-American Redistricting Coalition. A voluminous record was created.
In its final form, the plan ultimately adopted and filed by the Commission is not discernibly different, in terms of compactness, from the plan approved by this court in People ex rel. Burris v. Ryan, 147 Ill. 2d 270, 296 (1992), following the last federal decennial census. The similarity of compactness was confirmed by quantitative analysis. Cole-Randazzo, 198 Ill. 2d at 237-38. While some of the districts are certainly less compact than others, we pointed out in Cole-Randazzo, 198 Ill. 2d at 237, that the same was true of districts drawn under the previous map, which this court approved in People ex rel. Burris v. Ryan. Overall, the level of compactness has changed little.
In each of the eight cases now before us, plaintiffs contend that the districts drawn by the Commission after the latest census should nevertheless be rejected because alternative boundaries can be formulated that would be more compact. Our court has expressly held, however, that the ability to devise more compact formulations is not a sufficient basis for invalidating a map duly approved and filed according to law. Cole-Randazzo, 198 Ill. 2d at 238.
Under Illinois law, the issue of compactness cannot be considered in isolation. The formulation of redistricting plans involves complicated considerations requiring careful study and a weighing of factors. Donovan v. Holzman, 8 Ill. 2d 87, 93 (1956). As we noted in ColeRandazzo, 198 Ill. 2d at 236, compactness is but one of several different criteria that legislative and representative districts must satisfy. Districts must also be substantially equal in population, they must be configured in such a way as to provide adequate representation to minorities and other special interests protected by state and federal law, and they must meet all legal requirements regarding political fairness. Cole-Randazzo, 198 Ill. 2d at 236, citing People ex rel. Burris v. Ryan, 147 Ill. 2d 270, 296 (1992). No matter how compact a proposed district may be geographically, it will not suffice under the law unless it also complies with each of these additional factors. Cole-Randazzo, 198 Ill. 2d at 238.
Geography, climate, commerce and human behavior being what they are, the population of Illinois is not distributed in homogenous, evenly spaced cells or grids. Because of that, an insistence on narrow, exact or inflexible measures of compactness would make adherence to the additional requirements we have recognized virtually impossible. Accordingly, perfect or maximum compactness is not required. Districts need only be “reasonably compact.” People ex rel. Burris v. Ryan, 147 Ill. 2d at 282; People ex rel. Scott v. Grivetti, 50 Ill. 2d 156, 166 (1971).
In setting the boundaries for the redistricting plan at issue in this case, the Commission rigorously adhered to the equality of population requirement. That the Commission’s plan also provides adequate representation to minorities and other special interests protected by state and federal law is not questioned, nor is there any question that the plan conforms to legal requirements regarding political fairness. Under these circumstances, and considering the contours of some of the districts in the map previously approved by our court in People ex rel. Burris v. Ryan, we have no basis for holding that the districts challenged here are not reasonably compact.
Plaintiffs complain that the Commission’s plan will result in some units of local government being split into different districts, but a district does not fail the “reasonably compact” standard simply because its boundaries cut through or across local units of government, such as municipalities, villages, townships, cities and counties. Our court has long recognized that the boundaries of such units do not necessarily reveal communities of interest and that such units may have to be split for redistricting purposes in order for the resulting districts to meet the other requirements of law, particularly the requirement of equality of population. See Grivetti, 50 Ill. 2d at 166-67. We note, moreover, that the plan adopted by the Commission here actually resulted in far fewer splits of counties, townships and municipalities, on balance, than the map favored by the Commission’s Republican members and unsuccessfully offered to the Commission as an alternative to the map ultimately adopted.
Redistricting is a difficult and often contentious process. A balance must be drawn. Trade-offs must be made. In the end, the question turns on who is to make those assessments. Our predecessors on this court answered that question more than a century ago:
“Who, then, must finally determine whether or not a district is as compact as it could or should have been made? Surely not the courts, for this would take from the legislature all discretion in the matter and vest it in the courts, where it does not belong; and no apportionment could stand unless the districts should prove as compact as the judges might think they ought to be or as they could themselves make them. As the courts cannot make a senatorial apportionment directly, neither can they do so indirectly. There is a vast difference between determining whether the principle of compactness of territory has been applied at all or not, and whether or not the nearest practical approximation to perfect compactness has been attained. The first is a question which the courts may finally determine; the latter is [not].” People ex rel. Woodyatt v. Thompson, 155 Ill. 451, 480 (1895).
For the foregoing reasons, the requests by plaintiffs for a declaratory judgment invalidating the redistricting plan approved and filed by the Commission and for an order adopting the modified district boundaries proposed by plaintiffs are hereby denied. Judgment is entered for defendants. The mandate of this court shall issue immediately.
So ordered.
The legislators participating as plaintiffs are Rep. Mark Beaubien (R., 52nd Rep. Dist.), Rep. Raymond Poe (R., 99th Rep. Dist.), Rep. Rosemary Mulligan (R., 55th Rep. Dist.), Rep. Patricia Linder (R., 65th Rep. Dist.), Rep. Mike Bost (R., 115th Rep. Dist.), Rep. Rick Winkel (R., 103rd Rep. Dist.), Rep. Tom Berns (R., 104th Rep. Dist.), and Rep. Anne Zickus (R., 48th Rep. Dist.).
A challenge to the constitutionality of the procedure by which the ninth member of the Commission was selected was considered and rejected by a three-judge panel of federal judges in Barnow v. Ryan, No. 01 — CV—06566 (N.D. Ill, September 28, 2001).