[6] The initial establishment of a county seat was Claquato in 1862, the honor being relinquished in 1874 in favor of Chehalis.

Clockwise from the top left, those are: Grays Harbor, Thurston, Pierce, Yakima, Skamania, Cowlitz, Wahkiakum, and Pacific counties.

[11] One of the world's tallest Douglas fir trees was in the town of Mineral within Lewis County, attaining a height of 120 metres (390 ft).

Lewis County participates in the Point In Time Count (PTC), a census of the homeless population as required by law.

[24][25] Beginning in 2003 as mandated by the United States Department of Housing and Urban Development (HUD),[26] the annual PTC, which tracks the number of individuals and families experiencing homelessness on a specified date, is usually held in January.

In 2008 John McCain defeated Barack Obama by a margin of over 19 percent — his only victory in a county west of the Cascades.

[32] Since Washington's statehood in 1889 only three Democratic presidential candidates have carried the county – William Jennings Bryan in 1896, Franklin D. Roosevelt three times in 1932, 1936 and 1940, plus Lyndon B. Johnson in 1964.

[33] All told, as of 2025, 20 of the last 21 Republican presidential tickets successfully carried Lewis County, the only exception being that of Barry Goldwater who lost to the aforementioned Johnson.

It is part of Washington's 3rd congressional district, which has been represented by Democrat Marie Gluesenkamp Perez since 2023.

Patrolling several waterways in the county, including Riffe Lake and the Cowlitz River, the unit investigates boating accidents while providing water safety education, with an emphasis on the inspections of watercraft.

The county annually produces 600,000 short tons (540,000 t) of dried timber while hosting 10 pulpwood production plants.

[41] A leading economic producer for the county is farming,[42] with the region also holding large numbers for employment in mining, production, and warehousing.

Unemployment is perennially moderately higher than the state average, though boom years in large Lewis County economic sectors can influence the employment levels.

The cooperative, begun in 2003, showcases local artists, art studios and galleries throughout the region, and holds an annual autumnal studio tour that incorporates events in smaller towns within Lewis County.

[48][49] The Lewis County branch of the American Association of University Women (AAUW) has been in existence since 1923.

Located in the middle of Centralia, it is the oldest continuously operating community college in the state.

[52][53] The county honors the travels of pioneer Ezra Meeker on the Oregon Trail with several historical markers throughout the region.

The ride starts in Mary's Corner and through a variety of course options, participants can travel to several small towns and communities in the county and can bike through Centralia and Chehalis.

The project, meant specifically for rural residents in the county, is expected to be completed in late 2027.

[56] In late 2023, the county was announced as part of the Pacific Northwest Hydrogen Hub (PNW H2) initiative through the U.S. Department of Energy.

[60] The 22,000-acre (8,900 ha) site became operational in late 2020 and the energy produced is used through PSE's Green Direct program.