In 1844 Lewis was appointed by his brother-in-law GovernorBenjamin Fitzpatrick to the United States Senate to fill the vacancy caused by the resignation of William R. King in 1844. He was reelected as the Democratic candidate in 1847 and served from April 22, 1844, until his death in New York City on October 25, 1848. In the Senate he served as chairman of the Finance Committee from 1845 to 1847. He was appointed to the Board of Visitors of West Point in 1847.[2] Also in 1847 he bought at Baltimore "fifteen or twenty thousand dollars worth of Negroes for use of himself and his son, on their plantations, at home."[2]
A strikingly obese figure, Lewis was known to weigh as much as 500 pounds (227 kg), making him the heaviest member of Congress ever. A specially-constructed seat was provided in the Senate chambers for him, and his carriage was fitted with unusually heavy suspension springs. According to the WPAFederal Writers' Project publication Alabama: A Guide to the Deep South, a popular witticism among Lewis's colleagues was the observation that Alabama had the largest representation of any state.
^ ab"Dixon H. Lewis". The State Guard. 1847-08-03. p. 1. Retrieved 2023-09-18.
Alabama State Planning Commission. (1941) Alabama: A Guide to the Deep South. American Guide Series. Compiled by Workers of the Writer's Project of the Works Projects Administration in the State of Alabama.