In the late 1960s, Spokane's civic leaders were desperately looking for a way to revitalize a large section of downtown, especially a motley collection of little-used railroad lines and polluted industrial sites along the Spokane River. Their solution was to use the area for Expo '74, which was billed as the first ecologically themed world's fair. Critics predicted the project was sure to fail, as Spokane was the smallest city to ever host a world's fair, but history proved them wrong. From the minute the gates opened on May 4, 1974, the crowds loved the fair. Hosting 5.4 million visitors, with participation from several major companies and countries, Expo '74 was a success. As planned, it launched a rebirth along the river that left a permanent legacy, the popular Riverfront Park.