As development spread into south Minneapolis in the late nineteenth century, accidents at grade-level railroad crossings occurred with increasing frequency. The city battled to make the Chicago, Milwaukee, and Saint Paul Railroad (CM&StP) elevate or depress the double track of its Hastings and Dakota line paralleling Twenty-ninth Street. But the railroad resisted. After a series of lawsuits and appeals, the city prevailed before the U.S. Supreme Court in 1909.
Between 1912-16, the CM&StP dug a 2.8-mile long, 22-foot deep trench managing to keep its tracks in service the entire time. It built 37 reinforced-concrete bridges of essentially the same design to carry city streets over the depressed tracks. The project dramatically changed the south Minneapolis landscape and created a safer environment for the affected neighborhoods.
Rail use of the corridor ended in 1998. The grassroots Midtown Greenway Coalition successfully advocated government agencies to put the space to public use. Between 2000-06, the trench was repurposed as the Midtown Greenway, a 5.5-mile-long pedestrian-bicycle trail that includes the CM&StP trench and an at-grade rail corridor to the Mississippi River. SRF Consulting worked on preparing and implementing a master plan, owned by the Hennepin County Regional Railroad Authority which retains one side for possible mass transit use. The City of Minneapolis and county together maintain the trail. The county and city own most of the bridges, many of which are deteriorating and are gradually being replaced. About two dozen historic bridges remain.
The CM&StP Grade Separation District, running from Humboldt to Twentieth Avenues South, was listed in the National Register of Historic Places in 2005.
