Lincoln County is a county located in the U.S. state of Montana. As of the 2020 census, the population was 19,677. Its county seat is Libby. The county was founded in 1909 and named for President Abraham Lincoln. The county lies on Montana's north border and thus shares the US-Canadian border with the Canadian province of British Columbia.

This heavily wooded and mountainous county once was part of Flathead County until residents of Libby and Eureka petitioned the state legislature for separation. Libby won an election over Eureka to host the county seat.

According to the United States Census Bureau, the county has a total area of 3,675 square miles (9,520 km), of which 3,615 square miles (9,360 km) is land and 62 square miles (160 km) (1.7%) is water. The county borders the Canadian province of British Columbia to the north. The lowest point in the state of Montana is located on the Kootenai River in Lincoln County, where it flows out of Montana and into Idaho. Upstream, Libby Dam backs up huge Lake Koocanusa (combination name of Kootenai, Canada, USA) into Canada's British Columbia.

In 2003, the top employers are listed in the table below.

#	Employer	# of Employees
1	Kootenai National Forest	276
2	Libby Public School District	203
3	St John's Lutheran Hospital	182
4	Lincoln County Government	135
5	Owens & Hurst Lumber	120

Historical population

Census	Pop.	Note	%±
1910	3,638		—
1920	7,797		114.3%
1930	7,089		−9.1%
1940	7,882		11.2%
1950	8,693		10.3%
1960	12,537		44.2%
1970	18,063		44.1%
1980	17,752		−1.7%
1990	17,481		−1.5%
2000	18,837		7.8%
2010	19,687		4.5%
2020	19,677		−0.1%
2022 (est.)	21,525		9.4%
U.S. Decennial Census 1790–1960 1900–1990 1990–2000 2010–2020

As of the 2020 census, there were 19,677 people living in the county.

As of the 2010 census, there were 19,687 people, 8,843 households, and 5,608 families living in the county. The population density was 5.4 inhabitants per square mile (2.1/km). There were 11,413 housing units at an average density of 3.2 units per square mile (1.2 units/km). The racial makeup of the county was 95.9% white, 0.9% American Indian, 0.3% Asian, 0.1% black or African American, 0.4% from other races, and 2.3% from two or more races. Those of Hispanic or Latino origin made up 2.3% of the population. In terms of ancestry, 31.5% were German, 15.7% were Irish, 15.3% were English, 10.2% were Norwegian, and 3.3% were American.

Of the 8,843 households, 23.2% had children under the age of 18 living with them, 52.0% were married couples living together, 7.4% had a female householder with no husband present, 36.6% were non-families, and 30.6% of all households were made up of individuals. The average household size was 2.20 and the average family size was 2.72. The median age was 48.9 years.

The median income for a household in the county was $30,823 and the median income for a family was $39,600. Males had a median income of $40,944 versus $24,965 for females. The per capita income for the county was $19,626. About 13.7% of families and 18.6% of the population were below the poverty line, including 28.2% of those under age 18 and 12.1% of those age 65 or over.

• Libby (county seat)
• Troy

• Eureka
• Rexford

For its first eighty years, Lincoln County was a Democratic-leaning area that would vote Republican only during large GOP landslides. Only four Republicans were to win the county in the seventeen Presidential elections between its inaugural election in 1912 and 1976. However, like many timber-dependent counties, it has become overwhelmingly Republican since that time. The last Democrat to carry Lincoln County was Michael Dukakis during the drought-influenced 1988 election. Since then, no Democrat has reached 35 percent of the county's vote.

United States presidential election results for Lincoln County, Montana

Year	Republican		Democratic		Third party(ies)
	No.	%	No.	%	No.	%
2024	8,909	75.57%	2,615	22.18%	265	2.25%
2020	8,672	73.81%	2,835	24.13%	242	2.06%
2016	6,729	72.12%	2,041	21.88%	560	6.00%
2012	6,057	68.13%	2,552	28.71%	281	3.16%
2008	5,704	61.82%	3,025	32.78%	498	5.40%
2004	5,889	69.70%	2,320	27.46%	240	2.84%
2000	5,578	71.09%	1,629	20.76%	639	8.14%
1996	3,552	45.16%	2,705	34.39%	1,609	20.46%
1992	2,799	33.41%	2,765	33.00%	2,814	33.59%
1988	3,500	47.98%	3,601	49.37%	193	2.65%
1984	4,080	56.79%	2,959	41.19%	145	2.02%
1980	4,202	57.19%	2,422	32.96%	724	9.85%
1976	3,017	48.02%	3,146	50.07%	120	1.91%
1972	3,276	52.77%	2,402	38.69%	530	8.54%
1968	2,355	40.55%	2,677	46.10%	775	13.35%
1964	1,554	33.00%	3,140	66.68%	15	0.32%
1960	1,902	41.84%	2,623	57.70%	21	0.46%
1956	2,321	50.38%	2,286	49.62%	0	0.00%
1952	1,881	49.23%	1,907	49.91%	33	0.86%
1948	1,079	37.30%	1,689	58.38%	125	4.32%
1944	1,109	42.84%	1,445	55.81%	35	1.35%
1940	1,250	36.25%	2,150	62.35%	48	1.39%
1936	745	24.43%	2,117	69.41%	188	6.16%
1932	833	28.66%	1,867	64.25%	206	7.09%
1928	1,217	52.30%	1,067	45.85%	43	1.85%
1924	976	40.89%	374	15.67%	1,037	43.44%
1920	1,187	57.54%	683	33.11%	193	9.36%
1916	807	35.35%	1,186	51.95%	290	12.70%
1912	218	21.69%	346	34.43%	441	43.88%

• List of lakes in Lincoln County, Montana
• List of mountains in Lincoln County, Montana (A-L)
• List of mountains in Lincoln County, Montana (M-Z)
• National Register of Historic Places listings in Lincoln County MT

• Lincoln County, Montana

48°32′N 115°25′W / 48.54°N 115.41°W / 48.54; -115.41