MDOT maintains a listing of the historic bridges in the state; along US 31, the department has listed four structures. In downtown Charlevoix, the US-31–Island Lake Outlet Bridge carries the highway over a channel dredged between Lake Michigan and Round Lake that also connects to Lake Charlevoix. Built from 1947 through 1949, it is the fifth bridge at the location. It is a double-leaf bascule bridge. In Petoskey, the highway crosses Bear Creek on a concrete girder bridge built in 1930. At in length, it is the fourth longest such bridge in Michigan. In Manistee, the Manistee River is spanned by a double-leaf bascule bridge built in 1933. North of Hart in Pentwater Township, the US 31–Pentwater River Bridge is a long-span steel bridge that crosses the Pentwater River. It was listed on the National Register of Historic Places on December 20, 1999. It carries Oceana Drive along a former routing of US 31. Major intersections See also Business routes of U.S. Route 31 in Michigan Notes References External links US 31 at Michigan Highways 31 Michigan Freeways and expressways in Michigan Lake Michigan Circle Tour Transportation in Berrien County, Michigan Transportation in Van Buren County, Michigan Transportation in Allegan County, Michigan Transportation in Ottawa County, Michigan Transportation in Muskegon County, Michigan Transportation in Oceana County, Michigan Transportation in Mason County, Michigan Transportation in Manistee County, Michigan Transportation in Benzie County, Michigan Transportation in Grand Traverse County, Michigan Transportation in Antrim County, Michigan Transportation in Charlevoix County, Michigan Transportation in Emmet County, Michigan Transportation in Cheboygan County, Michigan