Isaac Deloss Barnum, Jr. (1825-1873) was a photographer in New York and Boston, Massachusetts in the mid-19th century. Around 1857 he kept a daguerreotype studio on Winter Street in Boston; by 1858 he had moved to Commercial Street. In 1856-1860 he lived in Roxbury. He participated in the 1860 exhibition of the Massachusetts Charitable Mechanic Association. He died October 7, 1873 in Cortland, New York.
Although a few records do exist that include his full name, he chose not to use it during most of his adult life. During his career as a photographer he was referred to by several variant names: D. Barnum; Deblois Barnum; Delos Barnum; DeLos Barnum; and Deloss Barnum.
From the Cortland County Standard and Journal, 7 October 1873: Died. Barnum - In this village, on the 1st inst., after a short illness, Mr. Delos Barnum, aged 48 years. The sudden departure of our friend has given a shock to the community; many of his associates not hearing of his illness until the rapid strides of disease had carried him past all hope of recovery. A faithful husband, a fond father, a genial citizen, and thoroughly honest and sincere nature, Delos Barnum will be greatly missed.