Following the decision to allow members of the Football Alliance into the Football League in 1892 the 'Second Division' was born.
Existing Football League teams became the First Division, remaining the "top tier" of English League football, with the old Alliance teams becoming the new second division. Newcastle were promoted to the Second Division from the Northern League, along with league winners Middlesbrough Ironopolis, at the end of the 1892-93 season.
By 1921, the Football League comprised of four divisions, outside of which many semi-professional and amateur leagues were formed and reformed. All leagues, and divisions of the Football Leagues, operating a system of promotion/relegation to gain admittance to the Football League and progression through it divisions, or regression down and out of the league.
This hierarchy remained in English football until 1992 when the 22 clubs making up the First Division elected to resign from the Football League and they create the Premier League.
The Football League itself was consequently re-organised, with the Second, Third and Fourth Divisions now becoming the First, Second and Third Divisions respectively. Thus, the First Division, while still the top level of the Football League, now became the second level of the entire English football league system.
NB: Prior to 1976 a system of "Goal Average" was used instead of the current "Goal Difference". The current 'goal difference' being goals scored minus goals conceded. Goal average being goals scored divided by goals conceded.