After several years working in business in the Philippines, Osborn took an interest in the Illinois Central Railroad in 1854. The Illinois Central, the first land grant railroad in the United States, was on the verge of bankruptcy in the wake of a stock scandal. A year after joining the railroad's Board of Directors, he was elected president, a position he held from December 1, 1855 to July 11, 1865.
Osborn became interested in the Chicago, St. Louis and New Orleans Railroad and guided the railroad from difficult economic times to profitability between 1875–1882. He retired from the railroad business in 1882 to concentrate on philanthropy near his home in Garrison, New York.