[3] It is named for Jesse Grimes, a signer of the Texas Declaration of Independence and early European-American settler of the county.

Like other tribes, they suffered high fatalities from new infectious diseases caught from the Spanish and joined with the remnants of other Native American people later in the historic period.

They were allowed them to practice their own religion, as long as they swore loyalty to the Mexican government.

A few historic buildings in Anderson, such as the Fanthorp Inn, date from this period, as well as some from the Republic of Texas and the early statehood years.

Early settlers were primarily from the South, especially Alabama, and many brought enslaved African Americans with them to work the land.

[5] Texas achieved its independence in 1836, and settlers arrived in greater numbers from the United States.

[5] Grimes County was organized in 1846, one year after the Republic of Texas agreed to be annexed by the United States.

Grimes had a total of 505 slaveholding families in 1860, with 77 owning 20 slaves or more, that number considered the minimum for major planters.

[5] In such conditions, Whites were anxious after the emancipation of slaves, and also struggled with adapting to a free labor market.

White violence rose after the war, and the Ku Klux Klan established a local chapter in 1868 to assert dominance.

[5] Determined to crush Populist efforts and alliances with Republicans that resulted in victories in 1896 and 1898, White Democrats formed what became the White Man's Union, a secret, oath-bound organization that violently took over elections in 1900, after killing several Black Populist leaders.

In the late 19th and 20th centuries, the Burlington Northern Santa Fe and the Union Pacific became the major railroads in the county.

In response to the violence and takeover by the White Man's Union, African Americans began to leave the county in large numbers.

These were periods of the Great Migration, as African Americans left Texas and other parts of the South to leave behind the oppression of Jim Crow and disenfranchisement, and seek better work.

The county remained mostly rural and agricultural until the late 20th century, which contributed to its continuing population losses.

The sheriff holds primary law enforcement responsibility over the county's unincorporated areas, and several cities covered under various interlocal agreements.