On August 20, 1845 the recently established Oregon Provisional Government created Clark County on the north side the Columbia River.
Actually the huge area was called the Vancouver District at first. It consisted of all the land south of Alaska, north of the Columbia, and from the Rockies to the Pacific Ocean.
In 1849 the district was renamed Clark County in honor of William Clark of Lewis and Clark, and encompassed all of present-day Washington for a time.
Nowadays Clark County is bounded on the north by the Lewis River, east by the Cascades and Skamania County, and on the west by the Columbia river and Cowlitz County.