[6] The Civil War era saw Atchison County as a center of pro-slavery sentiment, yet it also contributed soldiers to both sides of the conflict, reflecting the divided loyalties of the time.

The county's economy was significantly shaped by its river port facilities, which were vital for the steamboat trade and later for railroad development.

This infrastructure, combined with Kansas Statehood in 1861 and the end of the Civil War in 1865, boosted the local economy and made Atchison a key point for westward expansion.

[5] Moving into the late 19th century, Atchison County faced challenges like economic downturns and natural disasters, including floods, but it continued to grow as an industrial and agricultural center.

The county became known for its flour milling, due to its proximity to wheat fields, and its manufacturing industries, particularly after the Civil War, when life normalized, and new enterprises sprang up.

On July 4, 1804, to mark Independence Day, the Lewis and Clark Expedition named Independence Creek (River) located near the city of Atchison (see Timeline of the Lewis and Clark Expedition).

Sources: National Atlas,[8] U.S. Census Bureau[9] Atchison County comprises the Atchison, KS Micropolitan Statistical Area, which is also included in the Kansas City-Overland Park-Kansas City, MO-KS Combined Statistical Area.

Atchison County was a prohibition, or "dry", county until the Kansas Constitution was amended in 1986 and voters approved the sale of alcoholic liquor by the individual drink with a 30% food sales requirement.

The city of Atchison is considered governmentally independent and is excluded from the census figures for the townships.