Major League Baseball had 16 teams from 1901 through 1960, and then, for a number of reasons including population increases, the threat of a third major league being created and the availability of jet air travel, began expanding through the 1960s. Eight teams were added by 1969 and two more in 1977, 1993 and 1998, bringing us to the current total of 30.
So now it’s been 23 years since the last expansion and there are quite a number of cities that could qualify for MLB status. Some of these cities are actively lobbying for a MLB expansion franchise.