When Joseph Underwood Eldredge Sr was born on 10 October 1843, in Dennis, Barnstable, Massachusetts, United States, his father, Elnathan Eldredge III, was 32 and his mother, Ruth Baker, was 33. He married Vianna Merrill Pratt on 30 October 1870, in Salt Lake City, Salt Lake, Utah, United States. They were the parents of at least 4 sons and 5 daughters. He lived in Meadowville, Rich, Utah, United States in 1880 and Salt Lake, Utah, United States for about 20 years. He registered for military service in 1867. He died on 26 July 1934, in Salt Lake City, Salt Lake, Utah, United States, at the age of 90, and was buried in Salt Lake City Cemetery, Salt Lake City, Salt Lake, Utah, United States.