The idea for a world’s fair in Spokane came in the late 1960s, when 17 acres of railroad land along the Spokane River was acquired as part of a plan to remove railroads from the riverfront and downtown area of the city. Construction on Expo ’74 began in 1972 with the construction of the largest structure, the $11,500,000 U.S. Pavilion, currently the IMAX theatre. Expo ‘74’s theme was the first to focus on the environment, and Spokane was the smallest city to host an international exposition.