Congress formed the Washington Territory in 1853. The first territorial governor, Isaac I. Stevens, set about making treaties with Native American tribes; these were effective to varying degrees. Americans fought against the Yakima in the 1850s and the Nez Percé in the 1870s, the latter featuring the famous retreat led by Chief Joseph.

Another armed conflict, the Pig War, took place in 1859. It began after the shooting of a pig, which the shooter claimed was trespassing. The root of the problem was uncertainty as to the boundary between Great Britain and the U.S. in the San Juan Islands, between Vancouver Island and the mainland. Armed forces of the two countries narrowly avoided coming to blows.

Another draw for settlers was gold, discovered in Swauk Creek in 1873. Prospectors soon found gold in Williams Creek as well, and the mining town of Meagherville was born.

The completion of a number of railroads, starting with the Cascade Railroad Company in 1858, were a great boon to the Washington economy. Railroad construction brought a large influx of Chinese workers. Relations between Chinese and Americans were troubled at times, descending into race riots in Seattle and Tacoma.

A pot of glue from a cabinet shop caught fire, sparking the Great Fire of Seattle, which left charred remains of many business and destroyed 64 acres of land. It occurred on June 6, 1889. Spokane also suffered from a large fire in this year, on August 4; that city had to be rebuilt as well.

A draft constitution had been drawn up in 1878 but not officially adopted; it served, however, as a draft for the official constitution that was approved. Washington became a state on Nov. 11, 1889; the capital was Olympia.