Born in 1814 in Gloucester County, New Jersey, he and his family came to Richmond in 1823. At the age of fifteen he became a clerk in the drug store of Dr. James Mendenhall, and after a year he went to Liberty, Indiana as a salesman for Dr. Mendenhall. After working for his brother, Mark, at his store in Washington, Indiana (now Greensfork), James had several mercantile endeavors in Richmond and Cincinnati until 1855 when his health failed. He returned to Richmond and farmed until, in 1863, he and twelve other businessmen, including his brother Mark, formed the First National Bank, only the 17th such institution chartered and the second in Indiana. He was elected president and remained in that position until 1902.
In 1865 Governor Oliver P. Morton named Reeves the first treasurer of the Board of Trustees of the Indiana Agricultural College, which later became Purdue University. He was involved in numerous other businesses, including the Champion Roller Milling Company, and served on the Richmond city council.