The Nationals had their roots in the MLL's charter franchise the
Rochester Rattlers. Before the
2009 season, part of the Rattlers' roster was transferred to the new Nationals' team; however, the name, colors, and history stayed behind in Rochester to be potentially used by a future MLL team. In November 2010, it was reported that the
Chicago Machine had moved to
Rochester, NY and resumed operation of the Rattlers franchise. The Nationals started play in the MLL on May 15, 2009 and won against
Washington Bayhawks 17–16. They won their first home game over the
Chicago Machine 15–11. The Nationals qualified for the playoffs as the second seed with a 7–5 record and the best offense in MLL with 184 goals for. The Nationals played their first playoff game against the
Long Island Lizards at
Navy–Marine Corps Memorial Stadium in
Annapolis, Maryland. Toronto won their semi-final matchup 14–13 thanks to a strong game by
Merrick Thomson scoring 4 goals. Toronto (at the time) went on to face the
Denver Outlaws in the
Steinfeld Cup Final. The Nationals were tied with the Outlaws 9–9 with over a minute to go in the game. Nationals head coach
Dave Huntley called a time-out to draw out a strategy. With 45 seconds left to go,
Joe Walters passed to
Shawn Williams and Williams scored the winning goal to give the Toronto Nationals their first championship victory 10–9 over the Denver Outlaws.
Merrick Thomson was named Playoff MVP and
Brodie Merrill won the
Major League Lacrosse Defensive player of the Year Award. In 2009 their home field was
BMO Field and for 2010 at
Lamport Stadium. On February 3, 2011, the Nationals announced that they would be moving to Hamilton and would be known as the Hamilton Nationals. ==Season-by-season==