The Slayers, along with the Connecticut Wildcats, were established in 2003 as expansion teams of the American National Rugby League (AMNRL).

through David Niu, President of the American National Rugby League, helped find keen players to organise a club in Washington, D.C. On making contact with Martin O'Donoghue, who had played on the United States National team American National Rugby League, the first club meeting was held with fellow New Zealanders, Americans, Australians, and British players living in the D.C and surrounding areas.

At this time most players were recruited from rugby union clubs from across the greater Washington area, and many of them were personal friends of O'Donoghue, who served as the team's first coach.

[2][3][4] On February 18, it was announced that players and staff from the Fairfax Eagles, another Washington-based team that ceased operations before the season, would join the Slayers to form a stronger club.

[8] They have a team partnership with the St George Illawarra Dragons of Australia's National Rugby League (NRL).