The 1850 US Census shows him as a laborer, living in New Geneva. The following obituary was found in a Uniontown, Pennsylvania microfilmed Newspaper, dated March 28, 1878. From the information provided, it would appear that Joseph died March 19, 1887.
"Joseph Barnum died at Greenfield, Washington county, Pa., on Tuesday, the 19th inst., of cancer of the stomach, Joseph Barnum, in the 57th year of his age. Deceased was born in George's township Fayette Co., Pa., and while a boy worked with his father, Samuel Barnum, at Fairchance Iron Works while it was owned and controlled by F. H. Oliphant, Esq. where he was well known. He married in this county, and removed to Greenfield several years ago, where he has lived ever since. He leaves a wife and five grown up children, three brothers and two sisters to morn his departure. One of his brothers (Jacob) lives at New Geneva, Pa."