After opening a law office in Monticello in 1939, he was elected Supervisor of the Town of Thompson for two terms.
In November 1961, he was elected unopposed a justice of the New York Supreme Court, and was appointed to the Appellate Division in 1968.
He retired from the bench at the end of 1984 when he reached the constitutional age limit of 70 years.
A number of events and places have been named in his honor, including the Annual Chief Judge Lawrence H. Cooke State Constitutional Commentary Symposium and the Lawrence H. Cooke Sullivan County Courthouse.
Tribute to Chief Judge Lawrence H. Cooke, 1914–2000, by Vincent Martin Bonventre, Albany Law Review, vol.