The MSHD started studies for a freeway routing of US 31 from the state line northward to I-94 in 1967. The first section northward to Niles was approved in 1972, and the remainder of the route was approved in 1981. Since then, MDOT re-evaluated the St. Joseph Valley Parkway extension east of Benton Harbor, due to environmental, economic, and historical site issues. One of the environmental concerns that was studied relates to the habitat of an endangered species, the Mitchell's satyr butterfly, which has its habitat in the area of the proposed freeway. The habitat is home to the second-largest population of the rare butterfly. The freeway between Niles and Benton Harbor was planned as a series of five segments when approved in 1981. Since that approval, the butterfly was discovered in the Blue Creek Fen in the late 1980s, and it was listed as an endangered species in 1992. This listing stalled MDOT's planning and construction of the fifth freeway segment north of Berrien Springs. The United States Fish and Wildlife Service (USFWS) issued an opinion two years later that the project would jeopardize the species. MDOT was given permission to modify the previously approved freeway to cross the Blue Creek on longer bridges; the USFWS also required that any construction be done from elevated platforms, among other restrictions. In the interim, MDOT proceeded with construction of the southern portion of the last freeway segment, completing it northward from Berrien Springs to the Napier Avenue interchange in August 2003.