By 1954, the railroad began to realize it could sell more air rights and Grand Central Terminal was proposed to be replaced by a 50-story tower. This is how the Pan Am Building came to be built next to the station, after public protest regarding the demolition of Grand Central Terminal.[13] This approach has been used in Chicago since the construction of the Prudential Building in 1955 above active railroad tracks of the Illinois Central Railroad.[14] In 2017, to the west of the Chicago River, River Point and 150 North Riverside were built above tracks leading to the Amtrak station.