WASHINGTON -- Ross Detwiler allowed four hits in seven shutout innings and Adam LaRoche homered Monday, giving the Washington Nationals their first winning season with a 2-1 victory over the Chicago Cubs.

The NL East-leading Nationals improved to 82-52. The club moved from Montreal to Washington for the 2005 season and went 81-81 that year. In 2008 and 2009, the team lost a combined 205 games, then finished 80-81 in 2011.

The Nationals' win allowed them to hold their 6 1/2-game division lead over Atlanta.

Detwiler (9-6) struck out three and walked three, and allowed a runner to third only once.

Jeff Samardzija (8-13) gave up a long home run to LaRoche to lead off the second. LaRoche's 25th home run landed in the front row of the second deck. It's the fourth time in his career LaRoche has hit 25 or more home runs.

Ryan Zimmerman's RBI double scored Bryce Harper in the eighth for the second run.

Drew Storen pitched a perfect eighth.

Tyler Clippard allowed two hits and a two-out RBI single to Welington Castillo in the ninth. Clippard threw the ball away for an error and allowed pinch-runner Tony Campana advance to second before striking out Josh Vitters for his 30th save in 33 opportunities.

Samardzija gave up seven hits in seven innings. He walked one and struck out eight.

The Cubs, whose loss on Sunday guaranteed a third straight losing season, have dropped three straight.

NOTES: Nationals manager Davey Johnson, general manager Mike Rizzo and pitching coach Steve McCatty met with RHP Stephen Strasburg to explain the reasons the team is ending his season after two more starts. "I'm not sure any of us understand, but it's the right thing to do," Johnson said. ... Washington OF Michael Morse left the game in the fourth inning with a sore right thumb. ... Nationals LHP Sean Burnett will probably miss a few days with a sore right elbow, Johnson said. ... Washington purchased the contracts of RHP Christian Garcia and LHP Zach Duke from Triple-A Syracuse. RHP Henry Rodriguez was moved to the 60-day disabled list. ... U.S. Olympic swimming gold medalist Katie Ledecky threw out the first pitch. ... Nationals RHP Edwin Jackson (8-9, 3.53 ERA) and LHP Chris Rusin (0-1, 1.80) are Tuesday night's pitchers.