The Cubs, then known as the White Stockings, won the first-ever major-league championship by winning the National League's first pennant in its inaugural season of 1876. Their record was 52-14, some six games ahead of Hartford and St. Louis ( not connected with later St. Louis teams.) Thus, the Cubs currectly can claim the be both the first and last (so-far) MLB champions.

Although some consider the National Association of Professional Base Ball Players (1871-75) as a major league, it had an open-admission policy that included some very weak, semi-pro clubs that were barely minor-league level at best. The NL was the first professional league that restricted admission to a small number of well-financed clubs in strong markets, which is the basic definition of a major league.

The White Stockings ( direct ancestors of the Cubs) and the Red Stockings ( direct ancestors of today's Braves) were the only clubs to survive the NL 's first few years. Those Red Stockings won the NL's first-ever game, at Philadelphia.