Prior to 1949, Mission Bay was a 4000 acre marshland fed by the San Diego River. In 1949, the L.A. District of the Army Corps of Engineers and the City of San Diego jointly began construction of a small craft harbor and recreational facility. Three jetties were built along with dredging the navigation channels and small boat facilities. Dredged material was used to raise areas of the bay which had been semi-submerged. In the early 1950's the channel was closed to small boats because of repeated boating accidents from wave action at the entrance. In 1959, the channel was re-opened with the entire channel width dredged to -20 feet and 670 feet wide.