the costs involved, Pullman completed the first four production dome cars for GM's Train of Tomorrow in 1947. The four cars, dubbed Astra Liners, included a coach, diner, sleeper and lounge-observation., were similar to Silver Dome and were displayed to the press on numerous private charters and to the public at the Chicago Railroad Fairs in 1948 and 1949 before they were sold to Union Pacific Railroad for use between Portland, Oregon and Seattle, Washington. Other passenger car manufacturers soon built their own dome car models to compete with Pullman; Budd's first domes, completed in Fall 1947, were the first to feature curved glass and full streamlining effects on the domes and entered service on the Burlington's Twin Zephyrs between Chicago and Minneapolis-St. Paul. The Pere Marquette Railroad was the first to operate dome cars east of Chicago in 1948, and in 1949 Baltimore and Ohio Railroad became the first railroad to operate dome cars on the east coast when it introduced Pullman-built "Strata-Dome" coaches as part of the new consists for the Baltimore-Chicago Columbian. B&O also went so far as to add floodlights on the roofs of its dome cars to illuminate the scenery during nighttime travel. On September 14, 1950, a monument was established at Glenwood Canyon. Called "Monument to an Idea", this monument celebrated the Vista Dome at the place where it was first inspired. In the late 1980s, the monument was moved to the Colorado Railroad Museum in Golden, Colorado, to make way for expansion of Interstate 70. The first ten full-length domes were built by Pullman for the Milwaukee Road's Chicago-Seattle Olympian Hiawatha. The Milwaukee Road paid $320,000 each for their "Super Domes" and used them on that route until 1961, after which four cars remained in service between Chicago and the Twin Cities; these last four were sold to Amtrak upon its formation in 1971. Like most Pullman domes the Milwaukee domes were tall rather than the Budd/ACF standard . The Santa Fe and Great Northern also bought full-length domes from Budd in 1954 and 1955. All but one of Santa Fe's cars were sold to Auto-Train in 1971. As railroad passenger ridership declined in the late 1950s, some railroads retired dome cars due to the maintenance costs. Other railroads that had not purchased dome cars new bought them second hand. Illinois Central purchased several cars from Missouri Pacific and Canadian National bought several