The case of Stephen Baker Barnum, the patriarch of this family, is unique in that he apparently changed the spelling of his surname to Burnham later in life. That change is particularly interesting since the two surnames are quite distinct in the historical record and no other connection has been found between them.
Elbert was a real estate broker, in business with his brother Beekman T. Burnham. They were also neighbors in Yonkers in the 1870 US Census and both owned burial plots in Sandy Hills Cemetery in New Jersey. Their business address was 609 Hudson in 1869. Elbert's last known residence was 210 8th Avenue, New York, New York.
He was buried in Saint John Cemetery.