Tehama is most commonly believed to be derived from the Wintun word for "high water".

Others definitions of native origin that have been proposed such as "low land", "salmon", "mother nature" or "shallow".

A less accepted theory proposes the names origin is tejamanil, shingle in Spanish.

The first permanent non-indigenous settlers in the area that is now Tehama County were Robert Hasty Thomes, Albert Gallatin Toomes, William George Chard, and Job Francis Dye.

[6] Famous early figures include Kit Carson, who took part in a fight that gave name to Bloody Island and Battle Creek, Jedediah Smith, John C. Fremont, and William B. Ide, the first and only president of the California Republic.

[7] The January 29, 1886, edition of The Daily Alta detailed 'The Anti-Coolie Move' and confirms that a secret anti-Chinese meeting was convened in the town of Tehama, and an organization established to relocate the estimated 2,000 Chinese in and around Vina.

[10] A small part of Lassen Volcanic National Park extends into the northeast corner of the county.

The Shasta Regional Transportation Agency has proposed a weekday commuter bus to/from Red Bluff and the Sacramento Valley Station, following a route similar to the twice daily Amtrak Thruway 3.

The following table includes the number of incidents reported and the rate per 1,000 persons for each type of offense.

14.4% were of German, 11.0% English, 9.6% Irish and 9.5% American ancestry according to the 2000 United States census.

On November 4, 2008, Tehama County voted 72.7% for Proposition 8, which amended the California Constitution to ban same-sex marriages.