Washington Territory was a fallout region of the Oregon Treaty of 1846, which saw
the creation, on paper, at least, of
Oregon Territory. Soon after the treaty, settlers north of the
Columbia pushed for a separate territory, which came to pass in the US Congress in 1853, first
on a February bill as “Columbia Territory”, and then amended to “Washington Territory”
in March, in honour of the first US president, George Washington.
Washington Territory became the state it is today in 1889.