On April 6, 1917, Congress declared war. The Corps reassigned many Civil Works officers to military work. Lieutenant Colonel Schulz had already prepared for this event by reducing his District office staff to eight. During the summer of1917, lock and dam 1 was completed, and Minneapolis became head of navigation on the 6-foot Mississippi River channel. Above St. Anthony Falls, the steamboat LEE ceased to operate and navigation in the headwaters region came to an end. Logging on the St. Croix also ceased in 1917.