On July 7, 1851, at the superior court session on John Jackson's Cowlitz Valley farm, settlers took steps to call a convention to carve the Territory of Columbia out of Oregon, bounded on the south and east by the Columbia River, but including the Walla Walla Valley. The 24 members of the Columbia Territory Convention assembled at Cowlitz Landing -- also called Warbassport -- on August 29. The only settler from north of Olympia was Thomas Chambers of Steilacoom. The result was the assignment of Chapman to write a letter to Congress asking for a new territory.
Chapman's document spent more time criticizing the Hudson's Bay Company's monopoly in the region than on articulating the political advantages of a new territory. Congress did not act on the petition. A year later, settlers would assemble at the Monticello Convention in Lewis County and would again petition Congress. The result was a new territory named Washington.