Seacoast defense in the United States in the context of Chief of Engineers

Fort Mason, in San Francisco, California is a former United States Army post located in the northern Marina District, alongside San Francisco Bay. Fort Mason served as an Army post for more than 100 years, initially as a coastal defense site and subsequently as a military port facility. During World War II, it was the principal port for the Pacific campaign.

Fort Mason originated as a coastal defense site during the American Civil War. The nucleus of the property was owned by John C. Frémont and disputes over compensation by the United States continued into 1968. In 1882 the defenses were named for Richard Barnes Mason, a military governor before statehood. Fort Mason became the headquarters for an Army command that included California and the Hawaiian Islands from 1904 to 1907. In 1912 the Army began building a port facility with piers and warehouses to be a home base for ships of the Army Transport Service serving Alaska, Hawaii, the Philippines and other Pacific Army posts and focus of Army supply for the Pacific.

The columbiad was a large-caliber, smoothbore, muzzle-loading cannon able to fire heavy projectiles at both high and low trajectories. This feature enabled the columbiad to fire solid shot or shell to long ranges, making it an excellent seacoast defense weapon for its day. The columbiad was first made at the foundry of Henry Foxall on the Potomac in Georgetown for use at Fort Columbus on Governor's Island in New York. Columbiads were used in United States seacoast defense from the War of 1812 until the early years of the 20th century. Very few columbiads were used outside of the U.S. and Confederate Armies; nevertheless, the columbiad is considered by some as the inspiration for the later shell-only cannons developed by Frenchman Henri-Joseph Paixhans some 30 years later.

Fort Mills (Corregidor, the Philippines) was the location of US Major General George F. Moore's headquarters for the Philippine Department's Harbor Defenses of Manila and Subic Bays in early World War II, and was the largest seacoast fort in the Philippines. Most of this Coast Artillery Corps fort was built 1904–1910 by the United States Army Corps of Engineers as part of the Taft program of seacoast defense. The fort was named for Brigadier General Samuel Meyers Mills Jr., Chief of Artillery 1905–1906. It was the primary location of the Battle of Corregidor in the Japanese invasion of the Philippines in 1941–42, and of the recapture of Corregidor in February 1945, both in World War II.