http://www.census.gov/popest/topics/methodology.
Rank Geographic area Population Estimates Estimates Base Census 2000
July 1, 2006 July 1, 2005 July 1, 2004 July 1, 2003 July 1, 2002 July 1, 2001 July 1, 2000 April 1, 2000 April 1, 2000
                     
  California 36457549 36154147 35841254 35466365 35024517 34550466 34008499 33871653 33871648
                     
  COUNTY                  
1  Los Angeles County 9948081 9941197 9917538 9862088 9776424 9663083 9547850 9519330 9519338
2  Orange County 3002048 2992642 2983977 2961937 2932364 2898135 2857659 2846289 2846289
3  San Diego County 2941454 2936609 2933929 2921810 2901719 2864593 2824933 2813833 2813833
4  Riverside County 2026803 1945392 1868528 1781299 1694734 1620932 1560091 1545387 1545387
5  San Bernardino County 1999332 1964511 1914795 1861853 1809402 1762152 1719206 1709434 1709434
6  Santa Clara County 1731281 1705158 1685568 1679420 1679529 1692695 1686885 1682585 1682585
7  Alameda County 1457426 1451065 1452735 1459268 1466095 1471663 1450738 1443741 1443741
8  Sacramento County 1374724 1363423 1350861 1330044 1302102 1266762 1230401 1223499 1223499
9  Contra Costa County 1024319 1017644 1007254 999196 988997 977125 953769 948816 948816
10  Fresno County 891756 878089 865468 850360 832415 814910 802273 799407 799407
11  Ventura County 799720 796348 795838 790127 781049 768784 756772 753195 753197
12  Kern County 780117 756981 733784 712860 693125 675997 663864 661655 661645
13  San Francisco County 744041 741025 743852 752853 763400 775257 776885 776733 776733
14  San Mateo County 705499 701175 698912 699751 702566 708114 708641 707163 707161
15  San Joaquin County 673170 664796 649338 631227 612730 593184 568333 563598 563598
16  Stanislaus County 512138 505492 497231 490630 480313 465372 449933 446997 446997
17  Sonoma County 466891 466970 467862 467115 466065 465818 460513 458614 458614
18  Tulare County 419909 411131 400940 390948 381489 374154 368985 368021 368021
19  Solano County 411680 410786 411410 410857 409307 404405 397182 394513 394542
20  Monterey County 410206 412340 414538 414644 412158 408558 403244 401764 401762
21  Santa Barbara County 400335 400908 401669 402939 401870 400925 399755 399347 399347
22  Placer County 326242 316868 306151 293254 278920 264840 251343 248399 248399
23  San Luis Obispo County 257005 255538 254312 252974 252022 250858 247737 246681 246681
24  Santa Cruz County 249705 249420 250763 251506 253461 255409 255834 255600 255602
25  Marin County 248742 247103 245884 246627 247350 248494 247713 247289 247289
26  Merced County 245658 242249 236774 231406 225055 218273 211705 210554 210554
27  Butte County 215881 214153 212609 210985 208683 205924 203808 203171 203171
28  Yolo County 188085 185091 184182 181971 179566 174872 169798 168660 168660
29  Shasta County 179951 178970 177608 175373 171813 167226 163850 163256 163256
30  El Dorado County 178066 176319 172638 168986 165707 161379 157210 156299 156299
31  Imperial County 160301 155862 152167 149049 145774 143711 142545 142361 142361
32  Madera County 146345 142530 138895 133686 128918 125933 123675 123109 123109
33  Kings County 146153 143467 142187 138515 134535 131942 129835 129461 129461
34  Napa County 133522 132516 132364 131822 130138 127825 124656 124308 124279
35  Humboldt County 128330 128359 128232 127753 127378 126685 126343 126518 126518
36  Nevada County 98764 98263 97308 96154 95052 93868 92541 92033 92033
37  Sutter County 91410 89005 86744 84803 82372 80204 79207 78930 78930
38  Mendocino County 88109 88276 88320 88443 87608 86952 86438 86265 86265
39  Yuba County 70396 67144 64449 63607 62386 61392 60345 60219 60219
40  Lake County 65933 65157 64234 63343 62255 60610 58606 58309 58309
41  Tehama County 61686 60932 59931 58793 57643 56818 56163 56039 56039
42  Tuolumne County 56855 56898 56768 56685 55997 55264 54680 54504 54501
43  San Benito County 55842 56006 55953 56114 55714 55011 53871 53234 53234
44  Calaveras County 47722 46779 45623 44666 43113 41763 40731 40554 40554
45  Siskiyou County 45091 45066 44810 44576 44193 44089 44260 44301 44301
46  Amador County 38941 38434 37715 37301 36792 35835 35194 35100 35100
47  Lassen County 34715 34603 34518 34074 33556 33651 33769 33828 33828
48  Del Norte County 28893 28719 28290 27878 27536 27406 27483 27507 27507
49  Glenn County 28061 27683 27418 27235 26823 26434 26458 26453 26453
50  Colusa County 21272 20873 20448 19773 19394 19153 18842 18804 18804
51  Plumas County 21263 21409 21297 21164 21001 20899 20783 20824 20824
52  Mariposa County 18401 18058 17892 17773 17303 17156 17149 17130 17130
53  Inyo County 17980 18040 18217 18342 18290 17993 17926 17945 17945
54  Trinity County 14313 13917 13587 13482 13247 13016 13015 13022 13022
55  Mono County 12754 12712 12706 12832 13003 12898 12868 12853 12853
56  Modoc County 9597 9503 9566 9467 9352 9331 9422 9449 9449
57  Sierra County 3455 3405 3475 3539 3497 3529 3577 3555 3555
58  Alpine County 1180 1138 1192 1188 1217 1205 1207 1208 1208
Rank Geographic area Population Estimates Estimates Base Census 2000
July 1, 2006 July 1, 2005 July 1, 2004 July 1, 2003 July 1, 2002 July 1, 2001 July 1, 2000 April 1, 2000 April 1, 2000
Source: U.S. Census Bureau, Population Estimates Program More Tables and Information: Population Estimates Program NOTE: The April 1, 2000 Estimates Base reflects modifications to the Census 2000 population as documented in the Count Question Resolution program, updates from the Boundary and Annexation Survey, and geographic program revisions. An "(X)" for the Census 2000 value indicates a locality that was formed or incorporated after Census 2000 or was erroneously omitted from Census 2000. See Geographic Change Notes for additional information on these localities.
Geographic area Population
California 33871648
COUNTY
Alameda County 1443741
Alpine County 1208
Amador County 35100
Butte County 203171
Calaveras County 40554
Colusa County 18804
Contra Costa County 948816
Del Norte County 27507
El Dorado County 156299
Fresno County 799407
Glenn County 26453
Humboldt County 126518
Imperial County 142361
Inyo County 17945
Kern County 661645
Kings County 129461
Lake County 58309
Lassen County 33828
Los Angeles County 9519338
Madera County 123109
Marin County 247289
Mariposa County 17130
Mendocino County 86265
Merced County 210554
Modoc County 9449
Mono County 12853
Monterey County 401762
Napa County 124279
Nevada County 92033
Orange County 2846289
Placer County 248399
Plumas County 20824
Riverside County 1545387
Sacramento County 1223499
San Benito County 53234
San Bernardino County 1709434
San Diego County 2813833
San Francisco County 776733
San Joaquin County 563598
San Luis Obispo County 246681
San Mateo County 707161
Santa Barbara County 399347
Santa Clara County 1682585
Santa Cruz County 255602
Shasta County 163256
Sierra County 3555
Siskiyou County 44301
Solano County 394542
Sonoma County 458614
Stanislaus County 446997
Sutter County 78930
Tehama County 56039
Trinity County 13022
Tulare County 368021
Tuolumne County 54501
Ventura County 753197
Yolo County 168660
Yuba County 60219