US County Populations 2018

According to the most recent United States Census, Los Angeles County in California is the largest county in the nation, with a total population of 10,150,558 – an increase of 3.32% since 2010. Chicago's Cook County follows and, although very large in its own right, is half the size of Los Angeles County with 5,231,356 residents. Harris County in Texas, Maricopa County in Arizona, and San Diego County in California make up the rest of the top five – all have populations in excess of three million.

Statistics from 2018 show that a number of counties have had substantial population growths since 2010. Fort Bend County in Texas tops the list, with its population having grown from 590,286 in 2010 to 741,958 in 2018 – an increase of 25.69%. Three other counties in Texas are also in top five counties with increased populations. These are Denton County (with an increase of 21.23%), Collin County (19.53%) and Travis County (16.89%).

Conversely, while Wayne County is the most populous county in state of Michigan, it has seen its population decrease by 3.22% since 2010, from 1,815,069 to 1,756,598. Counties in two other midwestern states, Missouri and Ohio, have also had population decreases, although both are more modest. Ohio's Cuyahoga County has decreased from 1,278,200 to 1,253,454, representing a reduction of 1.94%, while St. Louis County, Missouri's population has decreased from 998,681 in 2010 to 998,216 in 2018. Just one county, Hartford County in Connecticut, shows exactly zero population change, with census figures reporting a population of approximately 895,500 in both 2010 and 2018.

County Name 2018 Population 2010 Population Growth (since 2010)
Los Angeles County10,163,5079,824,4903.45%
Cook County5,211,2635,199,4770.23%
Harris County4,652,9804,107,85413.27%
Maricopa County4,307,0333,824,64412.61%
San Diego County3,337,6853,103,7937.54%
Orange County3,190,4003,017,1165.74%
Miami Dade County2,751,7962,507,2289.75%
Kings County2,648,7712,510,8425.49%
Dallas County2,618,1482,372,25710.37%
Riverside County2,423,2662,202,00110.05%
Queens County2,358,5822,235,7645.49%
Clark County2,204,0791,952,90612.86%
King County2,188,6491,937,37812.97%
San Bernardino County2,157,4042,041,2345.69%
Tarrant County2,054,4751,817,41713.04%
Bexar County1,958,5781,722,79713.69%
Santa Clara County1,938,1531,786,5428.49%
Broward County1,935,8781,752,90710.44%
Wayne County1,753,6161,815,069-3.39%
New York County1,664,7271,589,2174.75%
Alameda County1,663,1901,513,4029.90%
Middlesex County1,602,9471,507,0286.36%
Philadelphia County1,580,8631,528,2713.44%
Sacramento County1,530,6151,421,6517.66%
Suffolk County1,492,9531,494,689-0.12%
Bronx County1,471,1601,388,1225.98%
Palm Beach County1,471,1501,323,75311.13%
Hillsborough County1,408,5661,233,55714.19%
Nassau County1,369,5141,341,9032.06%
Orange County1,348,9751,148,69617.44%
Franklin County1,291,9811,166,27410.78%
Hennepin County1,252,0241,154,2088.47%
Oakland County1,250,8361,202,9683.98%
Cuyahoga County1,248,5141,278,200-2.32%
Travis County1,226,6981,030,52219.04%
Allegheny County1,223,0481,223,897-0.07%
Fairfax County1,148,4331,086,7345.68%
Contra Costa County1,147,4391,052,7998.99%
Salt Lake County1,135,6491,032,9599.94%
Mecklenburg County1,076,837923,20216.64%
Wake County1,072,203906,88418.23%
Montgomery County1,058,810976,1408.47%
Fulton County1,041,423925,79712.49%
Pima County1,022,769981,5404.20%
St. Louis County996,726998,681-0.20%
Fresno County989,255932,2186.12%
Honolulu County988,650956,1933.39%
Westchester County980,244950,9643.08%
Pinellas County970,637916,4905.91%
Collin County969,603788,44222.98%
Milwaukee County952,085948,3020.40%
Marion County950,082904,5045.04%
Fairfield County949,921919,7493.28%
Bergen County948,406906,8794.58%
Duval County937,934865,6598.35%
Shelby County936,961928,5520.91%
Dupage County930,128918,1121.31%
Erie County925,528919,2240.69%
Gwinnett County920,260808,25413.86%
Prince George's County912,756865,6535.44%
Hartford County895,388895,504-0.01%
Kern County893,119841,1166.18%
San Francisco County884,363805,7709.75%
Pierce County876,764795,27810.25%
Macomb County871,375841,3263.57%
Hidalgo County860,661779,01510.48%
New Haven County860,435863,618-0.37%
Ventura County854,223825,2983.50%
Middlesex County842,798811,2173.89%
El Paso County840,410803,5114.59%
Denton County836,210666,75025.42%
Baltimore County832,468806,4053.23%
Worcester County826,116800,2903.23%
Montgomery County826,075800,9813.13%
Hamilton County813,822802,2791.44%
Essex County808,285784,6943.01%
Multnomah County807,555737,1829.55%
Snohomish County801,633715,39312.05%
Suffolk County797,939725,39810.00%
Oklahoma County787,958720,7249.33%
Essex County785,205745,4225.34%
San Mateo County771,410719,8997.16%
Jefferson County771,158742,0183.93%
Fort Bend County764,828590,28629.57%
Cobb County755,754689,5959.59%
Dekalb County753,253692,5728.76%
Monroe County747,642744,9060.37%
San Joaquin County745,424687,2918.46%
Lee County739,224620,46719.14%
Denver County704,621603,21816.81%
Lake County703,520704,275-0.11%
Norfolk County700,322673,0144.06%
El Paso County699,232626,83411.55%
Jackson County698,895674,8043.57%
District Of Columbia693,972605,04014.70%
Will County692,661678,7982.04%
Hudson County691,643636,3458.69%
Davidson County691,243627,97310.08%
Polk County686,483603,13513.82%
Bernalillo County676,773663,9991.92%