Lawrence was born in Burnt House, West Virginia, on the 4th of April, 1888 and he enlisted in the US Navy. He was a Seaman when he deployed in support of the Mexican Campaign and his actions there earned him the Medal of Honor. The citation reads:

On board the U.S.S. Florida, Sinnett showed extraordinary heroism in the line of his profession during the seizure of Vera Cruz, Mexico, 21 April 1914.

Lawrence received his Medal of Honor on the 15th of June, 1914 and he and his wife Dausy had three children. Lawrence Clinton Sinnett died on the 11th of June, 1962 at the age of 74 and he is buried with his wife in the Harrisville Independent Order of Odd Fellows Cemetery, Harrisville, West Virginia: Section 1N, Lot 23.