Another factor to go with welch's excellent summation is that the major areas of growth in the DC area in recent decades have been to the south (Prince William and Stafford Counties), west (Fairfax and Loudoun Counties) and northwest (Montgomery County) of DC, and thus farther away from Baltimore. Prince William County went from 22,000 in 1950 to 470,000 in 2019 and Stafford County from 12,000 in 1950 to 153,000 in 2019. Fairfax County went from 98,000 in 1950 to 1,147,500 in 2019, the City of Fairfax from 2000 in 1950 to 24,000 in 2019 and Loudoun County from 21,000 in 1950 to 414,000 in 2019. Montgomery County, especially along the Rockville-Gaithersburg-Germantown tech corridor, went from 164,000 in 1950 to 1,051,000 in 2019.
By contrast, the populations of the closer suburbs like Alexandria, Arlington and Falls Church have merely doubled. And Washington proper is smaller. On the northeast side, Prince George's County grew dramatically in the post-World War II era (from 89,000 in 1940 to 660,000 in 1970) but has been relatively stagnant since.
So while in the 1980s and early 1990s it was still reasonable for the Orioles to market themselves to the DC area, with the team store in McPherson Square for example, and expect to draw fans from DC, PG County, Arlington and Alexandria, as time went by, more people, and more importantly, the more affluent people, moved further and further away, with an entire urban area between them and Baltimore.
On the flip side, it might have made sense to build Jack Kent Cooke Stadium on the east side of DC when Baltimore did not have an NFL team, but the return of the NFL to Baltimore and the growth of DC away from Landover and PG County in general makes that look less wise.
