During World War I, Pick served with the 23rd Engineers in France. He served in the Philippines from 1921 until 1923 and helped organize The 14th Engineer Regiment Philippine Scouts, largely composed of Filipino soldiers. He was the Corps of Engineers' District Engineer in New Orleans during the Great Mississippi Flood of 1927, and he helped coordinate federal relief efforts. Pick was named Missouri River Division Engineer in 1942, and with William Glenn Sloan of the Bureau of Reclamation he co-wrote the Pick-Sloan Plan for controlling the water resources of the Missouri River Basin.