Mortenson Construction has topped out the U.S. Bank Stadium, future home of the Minnesota Vikings. Topping out is a major milestone celebrated when the highest or last steel beam is placed in a building under construction. Mortenson broke ground on the project 21 months ago and the stadium is now 75 percent complete and is set to open in July 2016. More than 11,000 tons of steel help make up the roof of the facility, including the 989-foot-long, 1,700-ton ridge truss, which stands 214 feet above the playing field. The stadium will seat 65,000 people and span 1.7 million square feet. Mortenson Construction and Thor Construction are managing the building project. The Minnesota Sports Facilities Authority will own and operate the stadium. In early 2013, the Vikings and the University of Minnesota negotiated a use agreement allowing the Vikings to play the 2014 and 2015 seasons at TCF Bank Stadium on the university’s campus.