The Nationals rookie was chosen to replace the injured Giancarlo Stanton on the National League roster for Tuesday's game in Kansas City, making him the youngest position player ever selected to the Midsummer Classic.
The only two players younger than Harper in an All-Star Game were Dwight Gooden (in 1984) and Hall of Famer Bob Feller (1938).
"No words can explain it right now," Harper said after the Nationals' 4-1 win against the Rockies on Saturday afternoon in Washington. "It's exciting to go. I'm excited to get there and be around all the top guys in the country, of course, and all the top guys in baseball."
Harper replaces Stanton after it was announced that the Marlins' first-time All-Star would require arthroscopic surgery on his ailing right knee.
Harper was one of five original candidates on the NL Final Vote ballot, which was trimmed to four when Chipper Jones was named as a replacement for the injured Matt Kemp. David Freese won the voting on Thursday, then second-place finisher Michael Bourn was chosen Saturday afternoon to replace Harper's teammate, shortstop Ian Desmond.
Desmond, who has been playing with a nagging left oblique injury, has not missed an inning of play since April 19 and is on pace to become the franchise's all-time home runs leader among shortstops, but it was decided this week it was more important he take the time to recuperate.
"It's just tough," Desmond said. "It's not something that you want to do -- withdraw your name from the All-Star Game. As tough as it sounds, it's harder to do, especially when you're selected by Tony La Russa personally."
Desmond was a manager's selection and one of now four Washington All-Stars selected to the game, including starting pitchers Gio Gonzalez and Stephen Strasburg. Together with Harper, the foursome makes up the largest contingent of Nationals players to be named All-Stars since the franchise moved to Washington in 2005.
Desmond, who said he will not attend the game in Kansas City, is 19-for-47 (.404) with 13 extra-base hits (seven doubles, a triple, five homers), 13 RBIs, 11 runs and 3 walks in his last 12 games. He is on pace to hit three times more home runs than his previous career-best (he has 16 already, six more than his high-water mark of 10, set in 2010).
"By no means is this an injury where I'm at home and crippled, by any means," Desmond said. "But you sneeze, you cough, I'm holding my kid, things like that -- I feel it. I think in the second half, it'd be nice to go into the second half knowing my body's 100 percent."
Harper said he was disappointed to find that Desmond wouldn't be joining the trio in Kansas City this weekend, but the phenom will be joined by plenty of rookies.
Harper and Wade Miley, both on the NL roster, join Oakland's Ryan Cook, Anaheim's Mike Trout and Texas' Yu Darvish -- the AL Final Vote winner -- as the largest group of rookies to participate in the All-Star Game, eclipsing the previous record of four in 2001 and '03.
Nineteen All-Stars have made the Midsummer Classic before the age of 21 (including Harper and Trout), and six are in the Hall of Fame: Mickey Mantle, Al Kaline, Frank Robinson, Jim "Catfish Hunter, Johnny Bench and Feller.
The 83rd Major League Baseball All-Star Game will be televised nationally by FOX Sports, in Canada by Rogers Sportsnet and RDS, and worldwide by partners in more than 200 countries via MLB International's independent feed. Pregame ceremonies begin at 7:30 p.m. ET. ESPN Radio and ESPN Radio Deportes will provide exclusive national radio coverage. MLB Network, MLB.com and Sirius XM also will provide comprehensive All-Star Game coverage.
Harper, hitting .283 with eight home runs, 25 RBIs and 43 runs, is just the ninth player in baseball history to hit as many as eight homers in a season at age 19, and the first since Ken Griffey Jr. in 1989
The 2010 No. 1 overall Draft pick was the NL's Rookie of the Month in May and has helped lead the Nationals to the NL's best record at 49-33 under manager Davey Johnson.
The skipper has a keen perspective on All-Star youths, having managed Harper in his debut season in Washington after breaking into the big leagues as a manager with Gooden in 1984.
"Doc was the best pitcher I ever had at that age, and Harper's the best position player I've ever had at that age," Johnson said. "Both are special. It's fun to watch them go out there and enjoy expressing their talent. You never know quite what to expect, but you know it's going to be special."