From the Commemorative Biographical Record of Fairfield County, Connecticut (published 1899) comes the following: "The son, David Beach Barnum, was reared in Newtown, where he clerked in the store of Henry Sanford. He became connected with the Adams Express Company, and "rose from the ranks" to be its treasurer, with headquarters in New York City, where his death occurred."
From the NY Times of May 10, 1886: David Beach Barnum, treasurer of the Adams Express Company, died yesterday at the Strathmore, 1672 Broadway. He was born in Newtown, Conn. in 1837 and came to New York in 1863. In that year he entered the service of the company and his connection with it lasted until his death. Mr. Barnum was a member of Saint Bartholomew's Church. He combined in a remarkable degree excellent judgment and force of character with an even temperament. He leaves a wife and an only daughter.