Unusually for a sports rivalry, it arises more from circumstances surrounding the history of baseball in the two cities, about 40 miles (64 km) apart yet considered different markets, than anything that has so far happened on the field between the teams.

Following that move, Orioles' owner Peter Angelos strongly opposed any attempt by Major League Baseball (MLB) to expand to Washington despite that city's larger market, arguing that both teams would suffer commercially and that the Orioles' protected market had legally expanded to Washington once the second Senators franchise moved.

After the former Montreal Expos moved to Washington for the 2005 season, the Nationals and the Orioles began a contentious business relationship over the Mid-Atlantic Sports Network (MASN) cable channel that carries telecasts of both teams' games, the only such arrangement in MLB.

In the early 2010s the Nationals claimed that they were not getting their full share of MASN revenue; MLB's arbitration panel agreed with them but the Orioles, rather than accept that result, took it to court instead.

The Orioles and Expos met one another in routine interleague play – without any connotation of a "rivalry" or other special association between the teams – during the 1997, 1998, 1999, 2000, and 2001 seasons.

The 2006 schedule thus became the first to include games between Baltimore and Washington as interleague "natural rivals," inaugurating the "Beltway Series."

1891 saw the first major league games between the two cities, with the enfranchisement of the first Washington Senators (originally the Statesmen) in the American Association.

At the formation of the American League in 1901, franchises were placed in both cities, with the original Washington Senators and an earlier Baltimore Orioles team among the eight charter members.

The ramifications of the way in which Major League Baseball and Angelos created the new network and the agreements behind its creation has led to ill feeling among some fans.

In order to overcome Angelos′ opposition to the Expos′ move to Washington to become the Nationals and to head off any potential litigation over the matter, Major League Baseball (which owned the Expos/Nationals franchise from 2002 to 2006) and Angelos struck a deal in 2005 to create MASN.

The Washington Post reported that the animosity between the teams over the television rights fee dispute may have played a role in the Orioles postponing two games of a three-game home series against the Chicago White Sox, playing the third game without allowing fans to attend, and moving a subsequent series with the Tampa Bay Rays originally scheduled to be played in Baltimore to Tampa Bay due to security concerns during the civil unrest in Baltimore following the death of Freddie Gray in April 2015.

during the anthem has become an established tradition that is valid at any sporting event anywhere in the Baltimore-Washington region and does not necessarily signify support for the Baltimore Orioles.

[29] Writing in The Washington Times, sports columnist Thom Loverro described Showalter's comment as a "foolish insult,"[30] and took the matter further, arguing that, from a historical perspective, the Orioles organization owed a great deal to the kindness of Washington baseball owners and fans, as the Orioles might never have existed if the owners of the original Washington Senators franchise, the family of Clark Griffith, had not agreed to allow the St. Louis Browns to relocate for the 1954 season to Baltimore, which was considered the Senators′ territory at the time.

[30] The Baltimore press reported Showalter's comment differently; for example, Alejandro Zuniga wrote in The Baltimore Sun that the MASN deal had made up to Angelos and the Orioles for their loss of business when the Expos relocated into the Orioles′ territory, and that the MASN deal had not prevented "plenty of Orioles fans from converting into supporters of their new, more local ballclub [i.e., the Nationals].

The Orioles, he added, would have played with a healthy lineup that evening that included center fielder Adam Jones and third baseman Manny Machado; Dylan Bundy, the Orioles′ best starter, would have been on the mound.

In contrast, the Nationals had planned for A. J. Cole, who had had only mixed success at the major-league level over the preceding three years, to make a spot start on May 11.

Sports reporters took away a clear impression that the Orioles believed that the Nationals had unnecessarily cancelled the game so as to avoid an unfavorable pitching matchup and facing the Orioles′ best lineup.

"[31] The Orioles and the Nationals have never agreed to a trade, which as Barry Svrluga writes "The groups that own the two teams have a deep and abiding loathing for each other.

Despite the marketing of the Beltway Series as a "Battle of the Beltways" and the animosity some Baltimore and Washington baseball fans feel toward one another's teams and cities, some observers – both sports journalists and fans – question whether a Nationals-Orioles rivalry truly exists, arguing that it is a "manufactured" rivalry born of the media, marketing, interleague play, and coincidental geographical proximity rather than history or the significance of the games, and that the Beltway Series lacks the meaning of true rivalries found elsewhere in MLB.

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.

[34] 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.

Since 2012, when both the Nationals and Orioles began to achieve real success, fan interest in both teams has increased and led to greater attendance, but no particularly significant game has arisen as part of the Beltway Series.

The Orioles suffered their first losing season since 2011 by finishing 75–87, tied for last place in the American League East.

In 2019, this rivalry became even more one-sided when the Nationals claimed a spot in the 2019 World Series against the Houston Astros, which they eventually won.

The Baltimore and Washington sports markets also call into question the extent to which fans view a rivalry as existing.

The Beltway Series tends to draw well in both cities, but this does not necessarily indicate that fans are attending to watch a chapter in a true rivalry between teams with a history of meaningful competition or animosity; many appear to view the series merely as an annual opportunity for low-key, good-natured competition between the teams and their fans for "bragging rights" in the Baltimore-Washington region.

From 2008[40] through 2013, however, MASN televised the Beltway Series using an unconventional concept in which mixed Orioles-Nationals broadcast booths covered each game.

In a February 26, 2014, statement announcing the change, MASN said, "The combined booth is an idea that's run its course, and with both teams possessing strong individual identities and playoff aspirations for 2014 the decision was made to give fans what they've been clamoring for – their individual team's broadcast partners calling the action as they would for any other game.