During this period, Seattle attempted to counter the decline of its downtown and the area immediately to the north by hosting the Century 21 Exposition, the 1962 World's Fair. The fair, given a futuristic science theme, was designed to leave behind a civic center, now known as Seattle Center, including arts buildings, the Pacific Science Center and the Space Needle, and serving also as a fairground. In addition, freeways were built to compensate for all this new growth for people to commute. Most of the Eastside (east of Lake Washington) and northern suburbs came into being during the Boeing boom, as did Interstate Highways (I-5 and I-90). I-5 neatly cut off Downtown Seattle from Capitol Hill and First Hill.