Cottrell was elected as a Democrat to the Twenty-ninth Congress to fill the vacancy caused by the resignation of William L. Yancey and served from December 7, 1846, to March 3, 1847.
He moved to Florida in 1854.
He served in the Florida Senate in 1865โ1885.
He was appointed collector of customs at Cedar Keys, Florida, and served until his death in that city September 7, 1885.
He was interred in Old Town Cemetery, Old Town, Florida.