ILLINOIS SWIMMING POOL INSTALLATION & SERVICE BUSINESSES

Adams, Alexander, Bond, Boone, Brown, Bureau, Calhoun, Carroll, Cass, Champaign, Christian, Clark, Clay, Clinton, Coles, Cook, Crawford, Cumberland, De Witt, Dekalb, Douglas, Dupage, Edgar, Edwards, Effingham, Fayette, Ford, Franklin, Fulton, Gallatin, Greene, Grundy, Hamilton, Hancock, Hardin, Henderson, Henry, Iroquois, Jackson, Jasper, Jefferson, Jersey, Jo Daviess, Johnson, Kane, Kankakee, Kendall, Knox, La Salle, Lake, Lawrence, Lee, Livingston, Logan, Macon, Macoupin, Madison, Marion, Marshall, Mason, Massac, Mcdonough, Mchenry, Mclean, Menard, Mercer, Monroe, Montgomery, Morgan, Moultrie, Ogle, Peoria, Perry, Piatt, Pike, Pope, Pulaski, Putnam, Randolph, Richland, Rock Island, Saint Clair, Saline, Sangamon, Schuyler, Scott, Shelby, Stark, Stephenson, Tazewell, Union, Vermilion, Wabash, Warren, Washington, Wayne, White, Whiteside, Will, Williamson, Winnebago, Woodford

Illinois has three major geographical divisions. Northern Illinois is dominated by Chicago metropolitan area, or Chicagoland, which is the city of Chicago and its suburbs, and the adjoining exurban area into which the metropolis is expanding. As defined by the federal government, the Chicago metro area includes several counties in Illinois, Indiana, and Wisconsin, and has a population of over 9.8 million. Chicago itself is a cosmopolitan city, densely populated, industrialized, the transportation hub of the nation, and settled by a wide variety of ethnic groups. The city of Rockford, Illinois's third-largest city and center of the state's fourth largest metropolitan area, sits along Interstates 39 and 90 some 75 miles (121 km) northwest of Chicago. The Quad Cities region, located along the Mississippi River in northern Illinois, had a population of 381,342 in 2011.

The midsection of Illinois is the second major division, called Central Illinois. It is an area of mainly prairie and known as the Heart of Illinois. It is characterized by small towns and medium–small cities. The western section (west of the Illinois River) was originally part of the Military Tract of 1812 and forms the conspicuous western bulge of the state. Agriculture, particularly corn and soybeans, as well as educational institutions and manufacturing centers, figure prominently in Central Illinois. Cities include Peoria; Springfield, the state capital; Quincy; Decatur; Bloomington-Normal; and Champaign-Urbana.[27]

The third division is Southern Illinois, comprising the area south of U.S. Route 50, including Little Egypt, near the juncture of the Mississippi River and Ohio River. Southern Illinois is the site of the ancient city of Cahokia, as well as the site of the first state capital at Kaskaskia, which today is separated from the rest of the state by the Mississippi River.[27][54] This region has a somewhat warmer winter climate, different variety of crops (including some cotton farming in the past), more rugged topography (due to the area remaining unglaciated during the Illinoian Stage, unlike most of the rest of the state), as well as small-scale oil deposits and coal mining. The Illinois suburbs of St. Louis, such as East St. Louis, are located in this region, and collectively, they are known as the Metro-East. The other somewhat significant concentration of population in Southern Illinois is the Carbondale-Marion-Herrin, Illinois Combined Statistical Area centered on Carbondale and Marion, a two-county area that is home to 123,272 residents.[27] A portion of southeastern Illinois is part of the extended Evansville, Indiana, Metro Area, locally referred to as the Tri-State with Indiana and Kentucky. Seven Illinois counties are in the area.

In addition to these three, largely latitudinally defined divisions, all of the region outside the Chicago Metropolitan area is often called "downstate" Illinois. This term is flexible, but is generally meant to mean everything outside the influence of the Chicago area. Thus, some cities in Northern Illinois, such as DeKalb, which is west of Chicago, and Rockford—which is actually north of Chicago—are sometimes incorrectly considered to be 'downstate'. Wikipedia