Kenilworth won its first Amateur League premiership in 1927, and thereby spoiled what would have been a good story - a decade completely dominated by just two clubs. In the ten years spanning 1920to 1929, University won five premierships and Semaphore Central four. The camaraderie that developed over the years between these two clubs, had its roots in this fabulous decade when ‘The Blacks’ and ‘Centrals’ swept all before them (apart from the ‘inconsiderate’ Kenilworth premiership in 1927).
The 1920s saw guernsey numbers introduced, replacement of an injured player allowed, interstate football played against the Victorian amateurs, a Challenge Final played at National Park, and Hugh Millard begin a 33-year reign as Secretary of the Amateur League.
An A2 grade was introduced in 1928. By 1929 the number of affiliated clubs had grown to thirteen with the entry of Henley and Grange, Y.M.C.A., Teachers' Training College, Prince Alfred OC, South Adelaide Ramblers, St. Augustine, St. Peters OC, Underdale and Scotch OC.
St. Peter's School and PAC had left along with Glenferrie and St. Francis Xavier, while East Adelaide, Prospect, Dulwich, Goodwood and Marryatville all came and went within the decade.