Steve Lombardozzi started the winning rally against Michael Schwimer (0-1) by singling with two outs, and 19-year-old Bryce Harper - the youngest player in the majors - drew his third walk of the game before Jayson Werth also walked to load the bases.
That brought up Ramos, who hit a 1-2 pitch to bring home Lombardozzi and set off a celebration, with his teammates streaming out of the dugout to greet him at first base.
In Chicago, Paul Maholm pitched six crisp innings for his third consecutive win, allowing one run and three hits to lead Chicago over Los Angeles.
Maholm (3-2) has won his last three outings after dropping his first two. He has given up three runs over 18 1-3 innings during the streak.
David DeJesus and Alfonso Soriano each had three hits to help the Cubs bounce back from a disappointing loss at Cincinnati. Pinch-hitter Joe Mather homered in the sixth.
In Denver, Eric Hinske had four hits, including a tiebreaking two-run homer in the 11th inning to lead Atlanta over Colorado.
After pinch-hitter Tyler Pastornicky singled to start the 11th, Hinske sent a 94-mph fastball from Edgmer Escalona (0-1) into the Rockies' bullpen for his first homer of the season.
Chad Durbin (2-0) worked his way out of a jam in the 10th to earn the win and Craig Kimbrel survived a shaky 11th for his ninth save in 10 chances. Kimbrel gave up an RBI groundout to Todd Helton before getting Michael Cuddyer to roll out to end the game.
In San Francisco, Aramis Ramirez broke out of his slump with a go-ahead, two-run single in the seventh inning and Milwaukee held on to beat San Francisco.
Jonathan Lucroy had a pair of hits and drove in two runs for the Brewers, who knocked around Tim Lincecum in the first then rallied against San Francisco's bullpen to send the Giants to their fourth straight loss, all at home.
Ramirez lined a single to left against loser Clay Hensley (1-3).
In New York, Cody Ransom hit a two-run homer and a go-ahead single in the eighth inning to help Arizona hand New York its fourth straight loss.
Paul Goldschmidt hit a tying, two-run double in the eighth off Jon Rauch (3-1) and Ransom followed with an RBI single.
Arizona starter Wade Miley allowed four runs in six innings. Brad Ziegler (1-1) gave up a hit in the seventh and David Hernandez got Josh Thole to line out to left with runners on first and third to end the eighth.
In Houston, Jose Altuve put Houston ahead with a three-run homer in the second inning and the Astros held on to beat St. Louis for their fourth straight win.
Houston starter Lucas Harrell (2-2) gave up seven hits and four runs in 5 1-3 innings. Closer Brett Myers allowed one hit in a scoreless ninth for his seventh save after three other relievers combined to pitch 2 2-3 scoreless innings.
Kyle Lohse (4-1), who started the season 4-0 for the first time in his career, had his worst outing of the season. He yielded seven hits and five runs - both season highs - in a season-low five innings.
In Pittsburgh, Johnny Cueto remained unbeaten, giving up seven hits in his first complete game of the season as Cincinnati beat Pittsburgh.
Cueto (4-0) struck out three without a walk to improve to 4-0 and lower his ERA to 1.32.
Zack Cozart and Drew Stubbs homered on consecutive pitches in the seventh inning off Pittsburgh starter Kevin Correia (1-2) to give Cincinnati plenty of breathing room. Jay Bruce later added his eighth home run of the season off reliever Chris Resop.
Nate McLouth, starting in center field in place of an ill Andrew McCutchen, had two hits for the Pirates but they failed to win consecutive games for the first time in three weeks.
In San Diego, Omar Infante doubled in the go-ahead run in the 12th inning to give Miami a win over San Diego.
Infante doubled to left-center off Josh Spence (0-1) with one out to score Hanley Ramirez, who led off with a walk. It was Infante's third hit and second RBI of the game.
Ramirez hit a three-run homer in a five-run first, and Giancarlo Stanton also connected.
Steve Cishek (4-0), the seventh Marlins pitcher, threw three scoreless innings for the win. With a runner on second, Jesus Guzman lined out to Infante at second base to end it.
Padres closer Huston Street left the game in the 10th with a right shoulder strain.
San Diego scored one run in the ninth off former closer Heath Bell to send the game into extra innings. It was Bell's fourth blown save in seven chances.
