The 20 Largest Counties in the US by population...
1) Los Angeles Co., CA 9,818,605(2010) 9,519,338(2000) +299,267
2) Cook Co., IL [Chicago] 5,194,675(2010) 5,376,741(2000) -182,066
3) Harris Co., TX [Houston] 4,092,459(2010) 3,400,578(2000) +691,881
4) Maricopa Co., AZ [Phoenix] 3,817,117(2010) 3,072,149(2000) +744,968
5) San Diego Co. CA 3,095,313(2010) 2,813,133(2000) +281,480
6) Orange County, CA [LA Metro] 3,010,232(2010) 2,846,289(2000) +163,943
7) Kings County, NY [NYC] 2,504,700(2010) 2,465,326(2000) +39,374
8) Miami-Dade Co, FL 2,496,435(2010) 2,253,362(2000) +243,073
9) Dallas Co., TX 2,368,139(2010) 2,218,899(2000) +149,240
10) Queens Co., NY [NYC] 2,230,722(2010) 2,229,379(2000) +1,343
11) Riverside Co. CA 2,189,641(2010) 1,545,387(2000) +644,254
12) San Bernadino Co., CA 2,035,210(2010) 1,709,434(2000) +325,776
13) Clark Co., NV [Las Vegas] 1,951,269(2010) 1,375,765(2000) +575,504
14) King Co., WA [Seattle] 1,931,249(2010) 1,737,034(2000) +325,776
15) Wayne Co., MI [Detroit] 1,820,584(2010) 2,061,162(2000) -240,562
16) Tarrant Co., TX [Ft. Worth] 1,809,034(2010) 1,446,219(2000) +362,815
17) Santa Clara Co., CA [San Jose] 1,781,642(2010) 1,682,585(2000) +99,057
18) Broward Co., FL [Ft. Lauderdale] 1,748,066(2010) 1,623,018(2000) +125,048
19) Bexar Co., TX [San Antonio] 1,714,778(2010) 1,392,931(2000) +321,842
20) New York Co., NY 1,585,873(2010) 1,537,195(2000) +48,678
http://2010.census.gov/2010census/data/
Another way to measure metro growth rates, and the size increase of county governments and influence