This is one of the first references I‘ve seen to a superhero—or, I suppose, super-hero. It’s from a 1915 newspaper, under a “standing of the clubs,” and in reference to Boston Braves catcher and first baseman Hank Gowdy:

A few things worth mentioning beyond “super-hero”:

• Gowdy was definitely super in the 1914 World Series against the Philadelphia A‘s. In four games and 16 plate appearances, this was his slash line: .545/.688/1.273. That’s eons ahead of his career line, .270/.351/.358, and the Boston Braves won in four. Then Connie Mack sold off all his best players. Above, they‘re tied for last in the AL. 
• “The Kissel Kar sign” was apparently an advert for this car company, which started in 1906, ended in 1942, and was headquartered in Wisconsin.
• The Fenway park. Wonder when they dropped the definite article. Also, the Braves used Fenway? For a time, according to Wiki: “...the Boston Braves used Fenway Park for the 1914 World Series and the 1915 season until Braves Field was completed.”
• Those quote marks around “Hank.” Love that. 
• “... perfectly legitimate income.” Because some didn’t think so? I guess we‘re never able to forgive athletes for being good enough to get paid to do what we do for fun.
• The 1915 World Series would be betweeen the second-place teams in the above standings, and feature the exact same cities but completely different teams: Instead of Boston Braves (NL) vs. Philadelphia A’s (AL) it was Boston Red Sox (AL) vs. Philadelphia Phillies (NL). Has that ever happened before? Red Sox won in five. The Phillies would be the last of the original 16 to finally win the World Series—65 years later in 1980. You gotta believe.

If anyone knows any earlier references to super-heroes, let me know.