Sports rivalries generally arise between teams that are familiar with one another, play one another frequently, and have a history of parity and of meeting one another in significant games, but this has rarely, if ever, occurred between Baltimore and Washington MLB teams. During the years from 1954 to 1971, when the Orioles played the original Senators and then the expansion Senators regularly in the American League, the Orioles enjoyed great success, while the two Senators teams between them managed only one winning season, in 1969. This unbalanced competition militated against any real rivalry springing up between the teams, as games between them tended to be insignificant and dominated by Baltimore. Moreover, memories of this era have faded with time as Baltimore- and Washington-area fans age and thanks to the transient nature of the Washington-area population, where the dominance of United States Government employment results in significant turnovers in population as people arrive to participate in government activities, then leave as political circumstances change.