Was that before or after the Football League was formed?
(and, on an obsessive point, didn't Blackburn Olympic win it just before Rovers?)
Before - 1884/5/6 and got a special trophy for the hat-trick of wins. Their first two wins were against Queen's Park, Glasgow and the last WBA. Blackburn Rover started life as Blackburn Grammar School Old Boys in 1874, which would appear to put a small spanner in the idea of them being representative of the working class. Blackburn Olympic won the cup in 1883, beating Old Etonians 2-1 in the final.