High Quality Content by WIKIPEDIA articles! 350 West Mart Center is the official name of the 24-floor multipurpose building located in the Near North Side community area of Chicago, at the intersection of the North Branch and the Main Branch of the Chicago River. Designed by Skidmore, Owings Merrill in 1977, the building is located in the River North district north of the Main Branch and east of the North Branch. In 1988, Helmut Jahn designed an enclosed pedestrian walking bridge over Orleans Street connecting the building to Merchandise Mart. Originally built to serve as the world`s largest wholesale buying center for the apparel industry, the building is more commonly known by several other names including Holiday Inn Chicago-Mart Plaza, Holiday Inn Mart, Merchandise Mart Annex, Merchandise Mart Annex Apparel Center, Apparel Mart, Chicago Apparel Center and Apparel Center. The building opened on November 6, 1976.