Elsie St. Leon (1884-1976) was one of the pre-eminent equestriennes of her day, a star of both circus and vaudeville. A third generation member of an Australian circus dynasty formed in the 1850s, she arrived in the U.S. in the 1890s with her parents and siblings. Elsie started off performing as a juggler at age seven, and later worked as an aerialist and rider with her family for Ringling Bros and Sells–Forepaugh and Coney Island’s Luna Park in the early years of the 20th century. It was said that Elsie was the only woman who could turn a somersault unattended whilst riding a horse bareback. Her horse was named “Swipe”. She and her family had a cameo in the 1913 film The Whimsical Threads of Destiny essentially playing themselves as circus riders. The St, Leon remain a going concern. One of their number, Mark St. Leon, maintains the wonderful circus history website The Pennygaff here.
While Elsie and her sister Vera were sometimes billed as the St. Leon Sisters, they are not to be confused with another pair of performing St. Leon Sisters, Elsie and Maude, dancers and comediennes on the New York stage in the 1860s.
To find out more about the history of vaudeville, consult No Applause, Just Throw Money: The Book That Made Vaudeville Famous, available at Amazon, Barnes and Noble, and wherever nutty books are sold.
And check out my new book: Chain of Fools: Silent Comedy and Its Legacies from Nickelodeons to Youtube, just released by Bear Manor Media, also available from amazon.com etc etc etc
(Travalanche) 
