The development and expansion of the Long Beach and Los Angeles Harbors in San Pedro Bay has been an ongoing effort involving dredging and associated landfill, construction of breakwaters and bulkheads, and other measures related to the conservation, development, and management of water and related land resources in the harbor area. The southwestern and midwestern sections of the United States are in a period of extensive growth, creating a need for an expanded port; increased use of containerization in shipping also requires more land in order to guarantee an efficient operation. Through extensive studies of historical, current, and projected use of the Ports of Long Beach and Los Angeles, it has been determined that San Pedro Bay will need an additional 2,600 acres of land to help handle the anticipated 223,210,000 short tons of cargo passing through the Ports by year 2020. This paper describe's the development of the Long Beach and Los Angeles Harbors from the late 1800's, when the area was a large expanse of mudflats and shallow water, to the present: the largest harbor complex along the west coast of the United States. A discussion of future developments is also presented. Particular attention will be given to the subjects of dredging and landfill and their important role in the development of the Port of Long Beach, and to the high regard given to mitigation trade-offs.