Born in the Waterloo section of Laurens County, O. Langdon Long graduated from the Citadel in 1914 with a B.S. degree. He read law while Principal of Edmunds High School in Sumter, and was admitted to the Bar in 1918. He practiced law in Laurens.
Active in civic affairs, he served as Mayor of Laurens, South Carolina State Senator from Laurens County, School Trustee, officer of the Methodist Church, a Democratic State Committeeman and a delegate to three National Democratic Party Conventions.
He served as President of the Laurens County Bar, and as a member of the Executive Committee of the South Carolina Bar from 1961 until 1964. He married Sarah Dwight who survived him with two children; their oldest son, Lieutenant Langdon Dwight Long was killed in World War II.
A courageous advocate, trusted counselor, and recognized leader of the Laurens Bar for a quarter-century, he was a respected member of the South Carolina Bar Association with trial law as his forte and the courtroom his forum. He sought no quarter and gave none, but fought fairly and vigorously and protected the interests of his clients.