The Amazons (1917)

The Marchioness of Castlejordan was so desperate to have sons that she raised her three daughters--Tommy, Willie and Noel--as boys. While on a trip to London the girls change into female clothes, but the youngest of them Tommy, changes into boys clothes and gets into a fight in a music hall, knocking out his opponent. Pursued by an angry mob, Tommy jumps into the nearest passing car, which happens to belong to Lord Litterly, who admires the "boy's" pluck. Litterly soon discovers that Tommy is actually a girl, and also discovers something else--she is a relative. Complications ensue.