The Beltway Series, promoted by the teams as "The Battle of the Beltways," is the Major League Baseball (MLB) interleague rivalry series played between the Baltimore Orioles and Washington Nationals. The Orioles are a member of the American League (AL) East division, and the Nationals are a member of the National League (NL) East division. The series name is taken from the beltway highways, the Baltimore Beltway (I-695) and the Capital Beltway (I-495), that serve Baltimore, Maryland, and Washington, D.C., respectively.

Unusually for a sports rivalry, it arises more from circumstances surrounding the history of baseball in the two cities, about apart yet considered different markets, than anything that has so far happened on the field between the teams. Washington's previous team, the Senators, had been AL regulars for most of the 20th century, but after their 1933 pennant often finished last or almost last in the standings. Within a decade of the AL St. Louis Browns' move to Baltimore to become the Orioles in the 1950s, the Orioles became pennant contenders while the Senators moved to Minnesota and became the Twins. A replacement Senators franchise fared little better either commercially or athletically, moving to Arlington, Texas and becoming the Texas Rangers within another decade. 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 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. The Orioles own the majority stake, with the Nationals beginning in 2005 as a 10% partner and their stake increasing one percent per year for 23 years until reaching a cap of 33 percent. 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.

History of the series

When interleague play began in , MLB identified the Philadelphia Phillies as Baltimore's interleague "natural rival," and the Orioles began an annual interleague series against the Phillies that season. At the time, the franchise that would become the Washington Nationals played in Montreal as the Montreal Expos, and the Expos played the Toronto Blue Jays as their interleague "natural rival" each year from 1997 to in what became known as the All-Canadian Series. 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 , , , , and seasons. The Expos posted a 9–6 record against the Orioles.

The relocation of the Expos to Washington for the season marked the first time the Baltimore–Washington Metropolitan Area had two Major League Baseball franchises since the season, after which the second Washington Senators franchise had moved to Arlington, Texas, to become the Texas Rangers. MLB changed the Orioles′ "natural rival" to the Nationals, but the Expos move to Washington came after the 2005 schedule already had been set. Thus, Baltimore and Washington did not face one another at all in 2005; the Orioles instead played the Phillies as their "natural rival" for the last time, while the Nationals played what would have been the Expos′ 2005 schedule, including six games against the Blue Jays that would have constituted the 2005 All-Canadian Series had the Expos remained in Montreal. The schedule thus became the first to include games between Baltimore and Washington as interleague "natural rivals," inaugurating the "Beltway Series."

Scheduling From through , the teams played each other six times a year, with one three-game series in each city and the two series taking place in May and June. The two series were separated by between three and six weeks.

From — when a realignment took effect in Major League Baseball's two leagues and their divisions — through , the schedule varied according to whether the American League East and National League East were scheduled to play one another in interleague play, which occurred on a rotational basis once every three years. During these seasons, the Beltway Series consisted of six games, with one three-game series in each city, played at any point during the season; in , for example, the teams played in Baltimore in July and in Washington in September. In seasons in which the two divisions did not meet, the Orioles and Nationals played four games, with a two-game series in each city. From 2013 to , the four games were played consecutively, but from onward, the four games were played in two two-game series that could take place at any point during the season.

In , the MLB schedule changed so that all MLB teams play each other each season. Under this new scheduling system, the Orioles and Nationals played each other four times in 2023 and , each hosting a two-game series. In , the series expanded to six games, with each team hosting a three-game series.

Overall results Through , the Orioles lead the Beltway Series in season series wins, 10–3–7, as well as overall wins 58–46.

Controversy fueling the rivalry

Controversy that fuels the Beltway Series rivalry revolves around various factors related to the unusual way in which the Washington, D.C. baseball market developed between the departure of the second Washington Senators team after the 1971 season and the arrival of the Nationals for the 2005 season because of the Orioles′ deep penetration of the Washington market during the era, as well as the circumstances under which the Expos relocated to Washington and the television deal MLB struck with the Orioles for coverage of Nationals games.

History of play between the cities Both cities have a long history of professional baseball, beginning with the 1871 Washington Olympics and the 1882 American Association Baltimore Orioles, followed by the 1886 Washington Nationals of the National League, which folded soon after the season. The first major-league games between the two cities took place in 1891, when the first Washington Senators (originally the Statesmen) began play in the American Association. The following season saw both teams join the National League. The two teams played 122 games, with the Orioles winning 79 to the Senators' 41, tying twice. The Baltimore and Washington National League teams both folded the season.

Upon the formation of the American League in 1901, franchises began play in both cities, with the original Washington Senators and a Baltimore Orioles team among the eight charter members. The Senators and Orioles played 40 times in those first two seasons, with the Orioles winning 22 to the Senators' 17, tying once. The original American League Orioles folded in 1902, and its remains became the foundation of the New York Highlanders, which began play in and eventually became the New York Yankees.

Play between Baltimore and Washington resumed in 1954 when the St. Louis Browns relocated to Baltimore and became the current Orioles, once again giving both cities teams in the American League and regular meetings each season. This second period of play between Baltimore and Washington lasted through the season. The original Senators moved to Minnesota after the season and became the Minnesota Twins and were replaced by a second Senators franchise, and expansion team which played in Washington from through the season. After the 1971 season, the second Senators franchise moved to Texas and became the Texas Rangers. The Orioles played 350 games combined against the two Senators franchises. Overall, the Orioles won the series with the Senators 224–126, which included an 89–65 mark against the original Senators and a 135–61 record against the second Senators franchise.

After the departure of the second Senators franchise, various efforts to return MLB to the Washington, D.C., area occurred, including a 1973 effort that almost relocated the San Diego Padres to Washington for the season, bids to purchase the Orioles in 1975 and the San Francisco Giants in 1976 and move them, a large "Baseball in Washington in ′87" promotion in 1987 advocating that a team to come to Washington, calls in 1991 and 1994 for MLB to place an expansion team in Washington, and efforts to buy the Pittsburgh Pirates in 1995 and the Houston Astros in 1996 for a move to Washington. None of these efforts bore fruit, and Washington, D.C., had no Major League Baseball team from 1972 through 2004. Play between Baltimore and Washington did not resume until the advent of the Beltway Series in 2006.

Opposition to relocation by the Orioles The Nationals–Orioles rivalry is influenced by circumstances surrounding the Nationals' founding. Peter Angelos, the owner of the Orioles, opposed the move of the Montreal Expos to Washington on the grounds that it would harm the Orioles financially, contending that the Orioles would lose fans to a Washington baseball team and that the Orioles alone had had a legal right to the entire Baltimore-Washington market since the departure of the second Senators team at the end of the 1971 season; in fact, the Orioles changed the team name on their away jerseys from "Baltimore" to "Orioles" in 1972 in an attempt to convince D.C. fans to adopt the Orioles as their "home" team. Ultimately, the owners of the other MLB teams approved the move to Washington in a 28–1 vote on December 3, 2004; Angelos cast the sole dissenting vote. The Orioles′ opposition to a baseball team in Washington created negative feelings among some Nationals fans toward the Orioles franchise, while some Orioles fans viewed the relocation of the Expos to Washington as an unwelcome intrusion that harmed the Orioles′ fan support and revenue. Even though the Nationals began play in 2005, the Orioles did not change the team name on their away jerseys back to "Baltimore" until 2009.

In the first four full seasons after baseball returned to Washington, the Nationals drew 9,127,252 fans to their games, compared to 8,892,951 fans attending Orioles games. The Nationals were a larger draw in , while both teams were about the same in (the Orioles drew exactly 100 more fans that year), and in the Orioles were a larger draw by nearly 200,000 fans. In the momentum swung back the Nationals' way, with the Nationals outdrawing the Orioles by over 370,000 fans, due in part to the opening of Nationals Park. In , the Orioles again drew better, attracting almost 90,000 more fans than the Nationals, but from through the Nationals outdrew the Orioles annually, ranging from an advantage of over 95,000 fans in 2010 to one of over 496,000 fans in 2017, and during the eight seasons from 2010 through 2017 combined the Nationals drew over 2,200,000 more fans than the Orioles. In 2018, as the Orioles struggled through a historically bad season, the Nationals outdrew the Orioles by over 965,000 fans.

"There are no real baseball fans in D.C."