He is primarily known as the owner of various baseball teams during the late 19th century, most notably the original Washington Senators.

Prior to their ownership of the Senators, Wagner and his brother were associates in the Armour meat-packing firm.

After the PL folded at the end of that season, Wagner joined a syndicate of PL owners, led by Al Johnson of the Cleveland Infants, that purchased the Cincinnati Reds.

Instead, Wagner settled for his own Athletics being admitted to the American Association for the 1891 season.

Wagner then purchased the Senators, another AA franchise which was brought into the National League.