List of Illinois Counties and County Seats

The U.S. state of Illinois is divided into 102 counties. Explore list of California Counties and their County Seats in alphabetical order and check their population, areas and the date of formation.

S.N	County	County Seat	Population(2011)	Area	Formed
1	Adams County	Quincy	67,103	857 sq mi	1825
2	Alexander County	Cairo	8,238	236 sq mi	1819
3	Bond County	Greenville	17,768	380 sq mi	1817
4	Boone County	Belvidere	54,165	281 sq mi	1837
5	Brown County	Mount Sterling	6,937	306 sq mi	1839
6	Bureau County	Princeton	34,978	869 sq mi	1837
7	Calhoun County	Hardin	5,089	254 sq mi	1825
8	Carroll County	Mount Carroll	15,387	444 sq mi	1839
9	Cass County	Virginia	13,642	376 sq mi	1837
10	Champaign County	Urbana	201,081	997 sq mi	1833
11	Christian County	Taylorville	34,800	709 sq mi	1839
12	Clark County	Marshall	16,335	502 sq mi	1819
13	Clay County	Louisville	13,815	469 sq mi	1824
14	Clinton County	Carlyle	37,762	474 sq mi	1824
15	Coles County	Charleston	53,873	508 sq mi	1830
16	Cook County	Chicago	5,194,675	946 sq mi	1831
17	Crawford County	Robinson	19,817	444 sq mi	1816
18	Cumberland County	Toledo	11,048	346 sq mi	1843
19	DeKalb County	Sycamore	105,160	634 sq mi	1837
20	DeWitt County	Clinton	16,561	398 sq mi	1839
21	Douglas County	Tuscola	19,980	417 sq mi	1859
22	DuPage County	Wheaton	916,924	334 sq mi	1839
23	Edgar County	Paris	18,576	624 sq mi	1823
24	Edwards County	Albion	6,721	222 sq mi	1814
25	Effingham County	Effingham	34,242	479 sq mi	1831
26	Fayette County	Vandalia	22,140	716 sq mi	1821
27	Ford County	Paxton	14,081	486 sq mi	1859
28	Franklin County	Benton	39,561	412 sq mi	1818
29	Fulton County	Lewistown	37,069	866 sq mi	1823
30	Gallatin County	Shawneetown	5,589	324 sq mi	1812
31	Greene County	Carrollton	13,886	543 sq mi	1821
32	Grundy County	Morris	50,063	420 sq mi	1841
33	Hamilton County	McLeansboro	8,457	435 sq mi	1821
34	Hancock County	Carthage	19,104	795 sq mi	1825
35	Hardin County	Elizabethtown	4,320	178 sq mi	1839
36	Henderson County	Oquawka	7,331	379 sq mi	1841
37	Henry County	Cambridge	50,486	823 sq mi	1825
38	Iroquois County	Watseka	29,718	1,116 sq mi	1833
39	Jackson County	Murphysboro	60,218	588 sq mi	1816
40	Jasper County	Newton	9,698	494 sq mi	1831
41	Jefferson County	Mount Vernon	38,827	571 sq mi	1819
42	Jersey County	Jerseyville	22,985	369 sq mi	1839
43	Jo Daviess County	Galena	22,678	601 sq mi	1827
44	Johnson County	Vienna	12,582	346 sq mi	1812
45	Kane County	Geneva	515,269	521 sq mi	1836
46	Kankakee County	Kankakee	113,449	678 sq mi	1853
47	Kendall County	Yorkville	114,736	321 sq mi	1841
48	Knox County	Galesburg	52,919	716 sq mi	1825
49	Lake County	Waukegan	703,462	448 sq mi	1839
50	LaSalle County	Ottawa	113,924	1,135 sq mi	1831
51	Lawrence County	Lawrenceville	16,833	372 sq mi	1821
52	Lee County	Dixon	36,031	725 sq mi	1839
53	Livingston County	Pontiac	38,950	1,044 sq mi	1837
54	Logan County	Lincoln	30,305	618 sq mi	1839
55	Macon County	Decatur	110,768	581 sq mi	1829
56	Macoupin County	Carlinville	47,765	864 sq mi	1829
57	Madison County	Edwardsville	269,282	725 sq mi	1812
58	Marion County	Salem	39,437	572 sq mi	1823
59	Marshall County	Lacon	12,640	386 sq mi	1839
60	Mason County	Havana	14,666	539 sq mi	1841
61	Massac County	Metropolis	15,429	239 sq mi	1843
62	McDonough County	Macomb	32,612	589 sq mi	1826
63	McHenry County	Woodstock	308,760	604 sq mi	1836
64	McLean County	Bloomington	169,572	1,184 sq mi	1830
65	Menard County	Petersburg	12,705	314 sq mi	1839
66	Mercer County	Aledo	16,434	561 sq mi	1825
67	Monroe County	Waterloo	32,957	388 sq mi	1816
68	Montgomery County	Hillsboro	30,104	704 sq mi	1821
69	Morgan County	Jacksonville	35,547	569 sq mi	1823
70	Moultrie County	Sullivan	14,846	336 sq mi	1843
71	Ogle County	Oregon	53,497	759 sq mi	1836
72	Peoria County	Peoria	186,494	620 sq mi	1825
73	Perry County	Pinckneyville	22,350	441 sq mi	1827
74	Piatt County	Monticello	16,729	440 sq mi	1841
75	Pike County	Pittsfield	16,430	830 sq mi	1821
76	Pope County	Golconda	4,470	371 sq mi	1816
77	Pulaski County	Mound City	6,161	201 sq mi	1843
78	Putnam County	Hennepin	6,006	160 sq mi	1825
79	Randolph County	Chester	33,476	578 sq mi	1795
80	Richland County	Olney	16,233	360 sq mi	1841
81	Rock Island County	Rock Island	147,546	427 sq mi	1831
82	Saline County	Harrisburg	24,913	383 sq mi	1847
83	Sangamon County	Springfield	197,465	868 sq mi	1821
84	Schuyler County	Rushville	7,544	437 sq mi	1825
85	Scott County	Winchester	5,355	251 sq mi	1839
86	Shelby County	Shelbyville	22,363	759 sq mi	1827
87	St. Clair County	Belleville	270,056	664 sq mi	1790
88	Stark County	Toulon	5,994	288 sq mi	1839
89	Stephenson County	Freeport	47,711	564 sq mi	1837
90	Tazewell County	Pekin	135,394	649 sq mi	1827
91	Union County	Jonesboro	17,808	416 sq mi	1818
92	Vermilion County	Danville	81,625	899 sq mi	1826
93	Wabash County	Mount Carmel	11,947	224 sq mi	1824
94	Warren County	Monmouth	17,707	543 sq mi	1825
95	Washington County	Nashville	14,716	563 sq mi	1818
96	Wayne County	Fairfield	16,760	714 sq mi	1819
97	White County	Carmi	14,665	495 sq mi	1815
98	Whiteside County	Morrison	58,498	685 sq mi	1836
99	Will County	Joliet	677,560	837 sq mi	1836
100	Williamson County	Marion	66,357	424 sq mi	1839
101	Winnebago County	Rockford	295,266	514 sq mi	1836
102	Woodford County	Eureka	38,664	528 sq mi	1841