In the 1900 US Census for District 89, Royalton, Niagara County, New York, Adelbert was enumerated in the household of his aunt Levanch Sherwood, as follows:
Dwelling #30; Family #32
Sherwood, Levanch; Head; White; Female; b. Feb 1858; 42; Single; b. New York; Both parents b. New York; Music teacher; Able to read, write, and speak English; Owns non-farm home free of mortgage
Barnum, Adalbert; Nephew; White; Male; b. July 1876; 23; Single; b. New York; Both parents b. New York; Salesman hardware; Able to read, write, and speak English
In the 1910 US Census for District 130, Porter, Niagara County, New York, Adelbert was a boarder with the family of Timothy J. Murphy and worked as a retail grocery merchant for his own account.
Adalbert and his brother Herbert Barnum were twins.
World War I Draft Registration Cards, 1917-1918 about Adelbert Jay Barnum. Name: Adelbert Jay Barnum; County: Niagara; State: New York; Birth Date: 29 Jul 1876; Race: White; FHL Roll Number: 1818602; DraftBoard: 2; Age: 42; Occupation: Merchant; Nearest Relative: Mrs. Hattie May Barnum; Height/Build: Medium/Medium; Color of Eyes/Hair: Light blue/Light Grey.