The Scarecrow of Romney Marsh had no actual super-powers, and can be seen as being the in the same tradition as other non-powered pre-Superman characters such as the Phantom. Christopher Syn's colorful and frightening alter ego may not have been a "super-hero" in this sense, but he was certainly a costumed crime fighter decades before Superman, Batman, et al.
From: "Superhero" article on Wikipeida" website (http://en.wikipedia.org/wiki/Superhero; viewed 11 January 2006):
Another early superhero was the Reverend Dr. Christopher Syn, the protagonist of a series of novels by Russell Thorndike. Dr. Syn adopted the masked and costumed identity of the Scarecrow of Romney Marsh to defend his parishioners against the King's press-gangs and tax agents. Set during the 1700s, Thordike's first novel featuring Dr. Syn/the Scarecrow was published in 1915, pre-dating the dual-identity superheroics of Superman, Batman and others by more than twenty years.