The 40 years between 1870 and 1910 marked a period of tremendous growth in Washington. In 1870, the territory’s population was just shy of 24,000; in 1910, the new state, created with the same boundaries, had 1,142,000 residents. Much of this growth was a direct result of the arrival of the Northern Pacific and Great Northern railways in the late 1880s, bringing industry and settlers to Puget Sound and creating new towns all along their routes. Spokane  saw rapid economic growth during the 1880s, outfitting miners for the gold, silver, and lead rush in Idaho.
The 1880s also spelled disaster for Spokane, Ellensburg , and Seattle , when major portions of these cities’ thriving downtown areas were destroyed by fire. Though the cities were rebuilt quickly in brick, the state was hit hard by a nationwide depression, the Panic of 1893, when growth slowed on both sides of the mountains and businesses failed. A gold rush in the Yukon and the emergence of hydroelectric power helped get the state back on its feet. At the end of this period of growth, the Alaska-Yukon-Pacific Exposition of 1909 brought nationwide attention and over 3.7 million visitors to what is now the University of Washington  campus in Seattle to promote the ties between Washington, the far north, and Pacific Rim countries.
The first and second World Wars changed Washington’s economy from one based largely on mining, farming, logging, and fishing to manufacturing and ship and airplane building, highlighted by Boeing’s B-17; over 13,000 of the “Flying Fortresses” were built for World War II. Boeing continues to be one of the state’s largest employers and most important industries and in the 1990s became America’s biggest exporter.
Seattle’s  1962 World’s Fair was the first such exposition to be an economic success, drawing almost 10 million people during its six-month run and creating a permanent addition to the city’s culture with the Seattle Center . Spokane  followed suit 12 years later with Expo ’74, emphasizing environmental concerns and cleaning up its own Spokane River in the process.