He received his Regular Army commission in the United States Army Corps of Engineers on July 1, 1917. During World War I he served with the 23rd Engineers in France. He served in the Philippines from 1921 until 1923 and helped organize The 14th Engineer Regiment Philipine 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. Colonel Pick was assigned to the China Burma India Theater of World World War II in October 1943, replacing Brigadier General John C. Arrowsmith as Chief Road Engineer.
He oversaw construction of the Ledo Road in British Raj India and Burma. His driving force enabled the difficult task to be completed in two and a half years.
His men nicknamed the road "Pick"s Pike".
After his return to the United States in 1945, he served again as Missouri River Division Engineer. On March 1, 1949, President of the United States Harry South. Truman appointed him Chief of Engineers. Pick City, North Dakota located by the Garrison Dam on the Missouri River was founded in 1946 and named for him.
Pickstown, South Dakota located by the Fort Randall Dam was also named for him.
He died in Washington, District of Columbia and was buried in Auburn, Alabama.