The first time shirts were numbered was on 25th August 1928, by Chelsea playing at home to Swansea, and by Arsenal who were playing at Hillsborough.

It wasn't tried again until the Cup Final of 1933 between Everton and Manchester City. One team wore 1-11 and the other 12-22.

The clubs voted on introducing shirt numbering in all League matches - but the vote failed, probably due to the usual reactionary forces within football, and clubs being faced with having to buy more shirts,

Numbering reappeared on the 1939 order paper, and managed to slip through as an instruction to clubs.
The Football League produced the instruction on how teams must be numbered..

2 Right Back
3 Left Back
4 Right Half Back
5 Centre Half Back
6 Left Half Back
7 Outside Right
8 Inside Right
9 Centre Forward
10 Inside Left
11 Outside Left

(The goalkeeper was omitted)

Numbers were to be no less than 8 inches long and lot less than 1 and a half inches wide.
As Wednesday played in blue and white striped, they were instructed to wear red numbers.

As the tactics of football changed, the numbers became associated with different position, but still linked to the original numberings, so 7 and 11 are the traditional numbers for wingers, 2 and 3 are the numbers for full backs etc.

Numbering in Programmes

The numbering harks back to the classic 2-3-5 formation which had come into vogue in the late 1870's, early 1880's .

Wednesday programmes printed the line up in the 2-3-5 formation, but they numbered players from 1-22, beginning with the Wednesday goalie as number 1 and the rest in the same order as above.

The earliest programme using this numbering (though the players themselves weren't wearing numbers) that I have seen comes from the 1903/4 season. The 1899/1900 season didn't seem to have the same numbering so it presumably came in at some point in-between.

Cobbled together from Simon Inglis - "League Football and the Men who made it" and Jason Dickinson's - "One Hundred Years at Hillsborough"