History 1920s–1980s. Between 1882 and 1924, Ireland was represented by a single national football team organised by the Belfast-based Irish Football Association (IFA). In 1920, Ireland was partitioned into Northern Ireland and the Irish Free State (the latter in turn becoming Éire or Ireland after adopting a new Constitution in 1937, followed by declaring itself a republic in 1949.)

https://en.wikipedia.org/wiki/Republic_of_Ireland_national_football_team