FIPS Code | State | County name | 2003 urban influence code | Description | 2000 population |
|---|
| 17001 | IL | Adams County | 8 | Micropolitan not adjacent to a metro area | 68,277 |
| 17003 | IL | Alexander County | 8 | Micropolitan not adjacent to a metro area | 9,590 |
| 17005 | IL | Bond County | 1 | Large-in a metro area with at least 1 million residents or more | 17,633 |
| 17007 | IL | Boone County | 2 | Small-in a metro area with fewer than 1 million residents | 41,786 |
| 17009 | IL | Brown County | 10 | Noncore adjacent to micro area and does not contain a town of at least 2,500 residents | 6,950 |
| 17011 | IL | Bureau County | 5 | Micropolitan adjacent to a small metro area | 35,503 |
| 17013 | IL | Calhoun County | 1 | Large-in a metro area with at least 1 million residents or more | 5,084 |
| 17015 | IL | Carroll County | 9 | Noncore adjacent to micro area and contains a town of 2,500- 9,999 residents | 16,674 |
| 17017 | IL | Cass County | 6 | Noncore adjacent to a small metro with town of at least 2,500 residents | 13,695 |
| 17019 | IL | Champaign County | 2 | Small-in a metro area with fewer than 1 million residents | 179,669 |
| 17021 | IL | Christian County | 5 | Micropolitan adjacent to a small metro area | 35,372 |
| 17023 | IL | Clark County | 6 | Noncore adjacent to a small metro with town of at least 2,500 residents | 17,008 |
| 17025 | IL | Clay County | 9 | Noncore adjacent to micro area and contains a town of 2,500- 9,999 residents | 14,560 |
| 17027 | IL | Clinton County | 1 | Large-in a metro area with at least 1 million residents or more | 35,535 |
| 17029 | IL | Coles County | 8 | Micropolitan not adjacent to a metro area | 53,196 |
| 17031 | IL | Cook County | 1 | Large-in a metro area with at least 1 million residents or more | 5,376,741 |
| 17033 | IL | Crawford County | 6 | Noncore adjacent to a small metro with town of at least 2,500 residents | 20,452 |
| 17035 | IL | Cumberland County | 8 | Micropolitan not adjacent to a metro area | 11,253 |
| 17037 | IL | DeKalb County | 1 | Large-in a metro area with at least 1 million residents or more | 88,969 |
| 17039 | IL | De Witt County | 6 | Noncore adjacent to a small metro with town of at least 2,500 residents | 16,798 |
| 17041 | IL | Douglas County | 6 | Noncore adjacent to a small metro with town of at least 2,500 residents | 19,922 |
| 17043 | IL | DuPage County | 1 | Large-in a metro area with at least 1 million residents or more | 904,161 |
| 17045 | IL | Edgar County | 6 | Noncore adjacent to a small metro with town of at least 2,500 residents | 19,704 |
| 17047 | IL | Edwards County | 12 | Noncore not adjacent to a metro/micro area and does not contain a town of at least 2,500 residents | 6,971 |
| 17049 | IL | Effingham County | 8 | Micropolitan not adjacent to a metro area | 34,264 |
| 17051 | IL | Fayette County | 4 | Noncore adjacent to a large metro area | 21,802 |
| 17053 | IL | Ford County | 2 | Small-in a metro area with fewer than 1 million residents | 14,241 |
| 17055 | IL | Franklin County | 9 | Noncore adjacent to micro area and contains a town of 2,500- 9,999 residents | 39,018 |
| 17057 | IL | Fulton County | 5 | Micropolitan adjacent to a small metro area | 38,250 |
| 17059 | IL | Gallatin County | 7 | Noncore adjacent to a small metro and does not contain a town of at least 2,500 residents | 6,445 |
| 17061 | IL | Greene County | 4 | Noncore adjacent to a large metro area | 14,761 |
| 17063 | IL | Grundy County | 1 | Large-in a metro area with at least 1 million residents or more | 37,535 |
| 17065 | IL | Hamilton County | 8 | Micropolitan not adjacent to a metro area | 8,621 |
| 17067 | IL | Hancock County | 9 | Noncore adjacent to micro area and contains a town of 2,500- 9,999 residents | 20,121 |
| 17069 | IL | Hardin County | 10 | Noncore adjacent to micro area and does not contain a town of at least 2,500 residents | 4,800 |
| 17071 | IL | Henderson County | 8 | Micropolitan not adjacent to a metro area | 8,213 |
| 17073 | IL | Henry County | 2 | Small-in a metro area with fewer than 1 million residents | 51,020 |
| 17075 | IL | Iroquois County | 6 | Noncore adjacent to a small metro with town of at least 2,500 residents | 31,334 |
| 17077 | IL | Jackson County | 8 | Micropolitan not adjacent to a metro area | 59,612 |
| 17079 | IL | Jasper County | 9 | Noncore adjacent to micro area and contains a town of 2,500- 9,999 residents | 10,117 |
| 17081 | IL | Jefferson County | 8 | Micropolitan not adjacent to a metro area | 40,045 |
| 17083 | IL | Jersey County | 1 | Large-in a metro area with at least 1 million residents or more | 21,668 |
| 17085 | IL | Jo Daviess County | 6 | Noncore adjacent to a small metro with town of at least 2,500 residents | 22,289 |
| 17087 | IL | Johnson County | 10 | Noncore adjacent to micro area and does not contain a town of at least 2,500 residents | 12,878 |
| 17089 | IL | Kane County | 1 | Large-in a metro area with at least 1 million residents or more | 404,119 |
| 17091 | IL | Kankakee County | 2 | Small-in a metro area with fewer than 1 million residents | 103,833 |
| 17093 | IL | Kendall County | 1 | Large-in a metro area with at least 1 million residents or more | 54,544 |
| 17095 | IL | Knox County | 5 | Micropolitan adjacent to a small metro area | 55,836 |
| 17097 | IL | Lake County | 1 | Large-in a metro area with at least 1 million residents or more | 644,356 |
| 17099 | IL | La Salle County | 3 | Micropolitan adjacent to a large metro area | 111,509 |
| 17101 | IL | Lawrence County | 9 | Noncore adjacent to micro area and contains a town of 2,500- 9,999 residents | 15,452 |
| 17103 | IL | Lee County | 3 | Micropolitan adjacent to a large metro area | 36,062 |
| 17105 | IL | Livingston County | 5 | Micropolitan adjacent to a small metro area | 39,678 |
| 17107 | IL | Logan County | 5 | Micropolitan adjacent to a small metro area | 31,183 |
| 17109 | IL | McDonough County | 8 | Micropolitan not adjacent to a metro area | 32,913 |
| 17111 | IL | McHenry County | 1 | Large-in a metro area with at least 1 million residents or more | 260,077 |
| 17113 | IL | McLean County | 2 | Small-in a metro area with fewer than 1 million residents | 150,433 |
| 17115 | IL | Macon County | 2 | Small-in a metro area with fewer than 1 million residents | 114,706 |
| 17117 | IL | Macoupin County | 1 | Large-in a metro area with at least 1 million residents or more | 49,019 |
| 17119 | IL | Madison County | 1 | Large-in a metro area with at least 1 million residents or more | 258,941 |
| 17121 | IL | Marion County | 3 | Micropolitan adjacent to a large metro area | 41,691 |
| 17123 | IL | Marshall County | 2 | Small-in a metro area with fewer than 1 million residents | 13,180 |
| 17125 | IL | Mason County | 6 | Noncore adjacent to a small metro with town of at least 2,500 residents | 16,038 |
| 17127 | IL | Massac County | 8 | Micropolitan not adjacent to a metro area | 15,161 |
| 17129 | IL | Menard County | 2 | Small-in a metro area with fewer than 1 million residents | 12,486 |
| 17131 | IL | Mercer County | 2 | Small-in a metro area with fewer than 1 million residents | 16,957 |
| 17133 | IL | Monroe County | 1 | Large-in a metro area with at least 1 million residents or more | 27,619 |
| 17135 | IL | Montgomery County | 6 | Noncore adjacent to a small metro with town of at least 2,500 residents | 30,652 |
| 17137 | IL | Morgan County | 5 | Micropolitan adjacent to a small metro area | 36,616 |
| 17139 | IL | Moultrie County | 6 | Noncore adjacent to a small metro with town of at least 2,500 residents | 14,287 |
| 17141 | IL | Ogle County | 5 | Micropolitan adjacent to a small metro area | 51,032 |
| 17143 | IL | Peoria County | 2 | Small-in a metro area with fewer than 1 million residents | 183,433 |
| 17145 | IL | Perry County | 9 | Noncore adjacent to micro area and contains a town of 2,500- 9,999 residents | 23,094 |
| 17147 | IL | Piatt County | 2 | Small-in a metro area with fewer than 1 million residents | 16,365 |
| 17149 | IL | Pike County | 9 | Noncore adjacent to micro area and contains a town of 2,500- 9,999 residents | 17,384 |
| 17151 | IL | Pope County | 10 | Noncore adjacent to micro area and does not contain a town of at least 2,500 residents | 4,413 |
| 17153 | IL | Pulaski County | 10 | Noncore adjacent to micro area and does not contain a town of at least 2,500 residents | 7,348 |
| 17155 | IL | Putnam County | 5 | Micropolitan adjacent to a small metro area | 6,086 |
| 17157 | IL | Randolph County | 4 | Noncore adjacent to a large metro area | 33,893 |
| 17159 | IL | Richland County | 11 | Noncore not adjacent to a metro/micro area and contains a town of 2,500 or more residents | 16,149 |
| 17161 | IL | Rock Island County | 2 | Small-in a metro area with fewer than 1 million residents | 149,374 |
| 17163 | IL | St. Clair County | 1 | Large-in a metro area with at least 1 million residents or more | 256,082 |
| 17165 | IL | Saline County | 8 | Micropolitan not adjacent to a metro area | 26,733 |
| 17167 | IL | Sangamon County | 2 | Small-in a metro area with fewer than 1 million residents | 188,951 |
| 17169 | IL | Schuyler County | 9 | Noncore adjacent to micro area and contains a town of 2,500- 9,999 residents | 7,189 |
| 17171 | IL | Scott County | 8 | Micropolitan not adjacent to a metro area | 5,537 |
| 17173 | IL | Shelby County | 6 | Noncore adjacent to a small metro with town of at least 2,500 residents | 22,893 |
| 17175 | IL | Stark County | 2 | Small-in a metro area with fewer than 1 million residents | 6,332 |
| 17177 | IL | Stephenson County | 5 | Micropolitan adjacent to a small metro area | 48,979 |
| 17179 | IL | Tazewell County | 2 | Small-in a metro area with fewer than 1 million residents | 128,485 |
| 17181 | IL | Union County | 9 | Noncore adjacent to micro area and contains a town of 2,500- 9,999 residents | 18,293 |
| 17183 | IL | Vermilion County | 2 | Small-in a metro area with fewer than 1 million residents | 83,919 |
| 17185 | IL | Wabash County | 6 | Noncore adjacent to a small metro with town of at least 2,500 residents | 12,937 |
| 17187 | IL | Warren County | 8 | Micropolitan not adjacent to a metro area | 18,735 |
| 17189 | IL | Washington County | 4 | Noncore adjacent to a large metro area | 15,148 |
| 17191 | IL | Wayne County | 9 | Noncore adjacent to micro area and contains a town of 2,500- 9,999 residents | 17,151 |
| 17193 | IL | White County | 6 | Noncore adjacent to a small metro with town of at least 2,500 residents | 15,371 |
| 17195 | IL | Whiteside County | 5 | Micropolitan adjacent to a small metro area | 60,653 |
| 17197 | IL | Will County | 1 | Large-in a metro area with at least 1 million residents or more | 502,266 |
| 17199 | IL | Williamson County | 8 | Micropolitan not adjacent to a metro area | 61,296 |
| 17201 | IL | Winnebago County | 2 | Small-in a metro area with fewer than 1 million residents | 278,418 |
| 17203 | IL | Woodford County | 2 | Small-in a metro area with fewer than 1 million residents | 35,469 |