As of the census of 2000, there were 26,507 people, 10,192 households, and 7,215 families residing in the county. The population density was 18 people per square mile (7/km²). There were 13,605 housing units at an average density of 9 per square mile (4/km²). The racial makeup of the county was 71.38% White, 0.12% Black or African American, 23.79% Native American, 0.30% Asian, 0.04% Pacific Islander, 0.67% from other races, and 3.70% from two or more races. 2.52% of the population were Hispanic or Latino of any race. 19.7% were of German, 8.8% Irish, 7.8% English, 5.4% Norwegian and 5.4% American ancestry according to Census 2000. 94.3% spoke English, 1.6% Salish and 1.2% Spanish as their first language.

There were 10,192 households out of which 33.00% had children under the age of 18 living with them, 54.80% were married couples living together, 11.50% had a female householder with no husband present, and 29.20% were non-families. 24.50% of all households were made up of individuals and 9.90% had someone living alone who was 65 years of age or older. The average household size was 2.54 and the average family size was 3.02.

In the county the population was spread out with 28.10% under the age of 18, 8.00% from 18 to 24, 24.50% from 25 to 44, 24.90% from 45 to 64, and 14.50% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 96.70 males. For every 100 females age 18 and over, there were 93.10 males.

The median income for a household in the county was $28,740, and the median income for a family was $34,033. Males had a median income of $27,009 versus $19,162 for females. The per capita income for the county was $15,173. About 14.00% of families and 18.70% of the population were below the poverty line, including 24.20% of those under age 18 and 8.30% of those age 65 or over.
 

Lake County Chambers of Commerce:

• Polson Chamber, P. O. Box 667, Polson, MT 59860, 406-883-5969
• Ronan Chamber, P. O. Box 254, Ronan, MT 59864, 406-676-8300
• St. Ignatius Chamber, P. O. Box 452, St. Ignatius, MT 59865-0452, 406-745-2190
• Swan Lake Chamber, P. O. Box 5199, Swan Lake, MT 59911, 406-886-2642

Lake County Economic Development:

• Lake County Community Development Corporation, P. O. Box 128, Ronan, MT 59864, contact Billie Lee, 406-676-5900
• Polson Community Development Association, P. O. Box 758, Polson, MT 59860,
  Contact Deborah Hayden, 406-883-8076
• Polson Redevelopment Agency, P. O. Box 1354, Polson, MT 59860, contact Todd Erickson at Lake County Job Service Workforce Center, 406-883-7885
• Salish Kootenai College Business Center, P. O. Box 117, Pablo, MT 59855, contact Nancy Warneke, 406-675-4800
   

Lake County Montana Motor Vehicle Division:

• Drivers' Licensing
  Polson -- 7 Third Ave. W., 406-883-3755

Lake County Newspapers:

• Char-Koosta News, P. O. Box 98, Pablo, MT 59855-0098, 406-675-3000
• Lake County Leader, P. O. Box 1090, Polson, MT 59860, 406-883-4343

Lake County Public Libraries:

• Jocko Valley Public Library, Highway 93 N., Arlee, MT 59821, 406-726-3572
• Polson City Library, 2 First Ave. E., Polson, MT 59860, 406-883-8225
• Ronan City Library, 203 Main St. SW, Ronan, MT 59864, 406-676-3682
• St. Ignatius School-Community Library, 4th and Blaine, St. Ignatius, MT 59865, 406-745-3811
• Swan Lake Public Library, Highway 83 South, Swan Lake, MT 59911, 406-886-2086
   

Lake County Montana Public Education:

• Superintendent of Schools, Kindergarten through 12th Grade:
• Arlee Public Schools, P. O. Box 37, Arlee, MT 59821, 406-726-3216
• Charlo Public Schools, P. O. Box 10, Charlo, MT 59824, 406-644-2207
• Polson Public Schools, 111 Fourth Ave. E., Polson, MT 59860, 406-883-6355
• Ronan Public Schools, Drawer R, Ronan, MT 59864, 406-676-3390
• St. Ignatius K-12 Schools, P. O. Box 1540, St. Ignatius, MT 59865, 406-745-4420
• Swan Lake-Salmon Elementary, Box 5086, Swan Lake, MT 59911, 406-886-2374
• Upper West Shore Elementary, P. O. Box 195, Dayton, MT 59914, 406-849-5240
• Valley View Elementary, 7000 Valley View Road, Polson, MT 59860, 406-883-2208