The North Dakota Memorial Bridge, later renamed the North Dakota Liberty Memorial Bridge, was the first automobile bridge in North Dakota to cross the Missouri River. Its roadway was designated State Highway 6 in 1922 and U.S. Highway 10 in 1926. The bridge honored the men and women who served and died in World War I. In 1924, the North Dakota chapter of the American War Mothers installed prairie boulders bearing memorial plaques at each end.
The structure used Warren-Turner trusses that spanned 200 feet above the bottom of the lowest pier. Workers drove 8,000 rivets into the trusses.
David Carey, his wife, and their four children arrived in 1879. John McGinley rowed them across the Missouri River in a skiff during a severe windstorm, and they nearly died. Carey had moved from Illinois to work on the Northern Pacific Railway bridge and helped build North Dakota's first railroad bridge across the Missouri.
When the automobile bridge opened, the 86-year-old Carey waited for hours so he could be the first person to cross it by car. “I am thankful I lived to see this day,” he said.
Concrete approaches lined with North Dakota-made brick extended 400 feet on the Bismarck side and 625 feet on the Mandan side. The bridge deck and approaches were 26 feet 6 inches wide, with pedestrian walkways 4 feet 4 inches wide. The eastern river pier extended about 41 feet below normal water level and 101 feet below the roadway. The western pier extended about 74 feet below the water and 134 feet below the deck.
Crews used the open-well method to construct the piers. Employment peaked at 250, with work continuing day and night. Ice and an unusually high June river rise each destroyed the temporary construction trestle once. Construction began in 1920, and a three-day dedication was held in September 1922. The $1,358,000 (about $21,825,000 in 2025 dollars) cost was shared by the federal government, North Dakota, and Morton and Burleigh counties.
The bridge initially connected Mandan and Bismarck as part of State Highway 6. The four-mile rural roadway ran from East Main Street in Mandan to Front Avenue and Hannifin Street in Bismarck. Bismarck's West Main Avenue reached that intersection through a three-block dogleg beneath a railroad viaduct. The route was paved with two lanes of concrete in 1924. On May 30, 1925—Memorial Day—it was dedicated as Memorial Highway in honor of Americans who died in military service.
Construction of a four-lane replacement began in 2006 after deicing salts corroded grout in the original stone piers. The new Liberty Memorial Bridge, dedicated November 11, 2008, honors all veterans who died in service. Explosive charges demolished the original bridge, which was removed from the riverbed in sections. Several additional efforts were needed to remove enough submerged material for safe boat passage.
A direct connection to the western end of Bismarck's Main Avenue opened in 1959. A viaduct about 200 feet southeast of the former grade crossing allowed Main and Rosser avenues to extend directly west beneath the railroad tracks.
Before 1959, most traffic east of the bridge followed Memorial Highway—West Front Avenue—and reached Main Avenue through the dogleg road and viaduct between Washington and Hannifin streets. The dogleg was eliminated during the 1994 Washington Street reconstruction, when new bridges were installed for Main Avenue and the railroad.