William E. Merrill graduated first in his class from the U. S. Military Academy in 1859 and was almost immediately involved in the Civil War. He fought in battles at Yorktown, Pa., Missionary Ridge, Chicamauga, Resaca, New Hope Church, and Perryville, Ky. Under U. S. Grant's command he devised a folding wood-and-canvas folding pontoon. He also designed and supervised the construction of 200 blockhouses protecting railroad bridges.
He was the author of two text-books, Iron Truss Bridges for Railroads, and Improvement of Non-Tidal Rivers.
In the command of James Milnor Roberts he served in the Cincinnati and Louisville offices of the U. S. Engineers, specializing in river improvement from 1870 until his death in 1891. He dropped dead on a railroad train en route to make an inspection at Shawneetown, Ill.
In 1873-74 he went to France to study locks and dams on the Marne, Yonne, Meuse and Seine Rivers. Upon his return he designed improvements to the movable dams invented by Chanoine and recommended them for use on American Rivers. He superintended the construction of the first Ohio River lock and dam at Davis Island. He invented the rolling lock gate. Davis Island Lock was the biggest in the world when it was constructed. This was the start of the river control project to provide a 9-foot channel below Louisville and a 6-foot channel above there to Pittsburgh. Similar projects were started on the Allegheny, Monongahela, Muskingum, Kanawha, Kentucky, and Green Rivers.
Late in his career he was involved in flood control projects to hold water in tributaries, a project that continues to this day.