This illustration of the 1872 Scotland v England match shows the players wearing 'knickerbockers', trousers that were tucked into the stockings. Some players of this era (Kinnaird notably) wore ordinary trousers.
By 1891 there was a slight shortening, but the knickers were still below knee length, as we can see in this illustration of the FA Cup Final between Blackburn Rovers and Notts County.
In the early 20th century Manchester United's Charlie Roberts was a trend setter, wearing what were considered indecently short knickers. Roberts' was an extreme case and most players persisted with knee length shorts.
Female footballers in 1920 had a distinctly modern appearance. This must have represented considerable novelty appeal to the onlookers.
1936- Harry Hooper (Sheffield United) wears shorts that would not look out of place today. Alex James ( Arsenal ) sports his trademark voluminous pants (I hesitate to use the word 'shorts').