PHILLIES — Johnny Lush (18 years, 336 days on Sept. 8, 1904)
Lush played games in his first season in 1904 as a first baseman, outfielder and pitcher. He hit two career home runs, and both were in 1904 while playing first base — and they were within a few days of each other, on Sept. 8 and 12. Not only that, both of the home runs were of the inside-the-park variety. The first was at the New York Giants, off Claude Elliott.
Runners-up: Ted Kazanski (19-175), Sherry Magee (20-33)
BREWERS — Robin Yount (18 years, 209 days on April 13, 1974)
The future Hall of Famer homered in his sixth career game off the Orioles’ Ross Grimsley. Oddly enough, Yount’s first two homers both came off Grimsley, even though one was in mid-April and the next was in mid-June. Yount went on to hit 251 career home runs, win two MVP Awards and was inducted into the Hall of Fame in 1999.
Runners-up: Darrell Porter (19-240), Gary Sheffield (19-296)
CARDINALS — Dick Schofield (18 years, 221 days on Aug. 16, 1953)
Schofield played for 19 years, amassing 3,545 plate appearances, but hit just 21 home runs in his career. His first one was historic for the franchise, though, as he hit it as an 18-year-old. He hit that first home run in Cincinnati off Frank Smith, in his 13th career game.
Runners-up: Bunny Hearn (19-142), Tim McCarver (19-270)
CUBS — Danny Murphy (18 years, 21 days on Sept. 13, 1960)
Murphy played outfield initially in his career, then finished up his final two seasons as a pitcher — but this home run, of course, came while he was an outfielder at just 18 years old. He actually debuted as a 17-year-old that year, but didn’t go yard until after his Aug. 23 birthday. His first home run came in his 21st career game. He hit it off the Reds’ Bob Purkey, a three-run home run to give the Cubs the lead in a game in Cincinnati. Murphy hit four career home runs, including his fourth and final one as a pitcher in 1970.
Runners-up: Phil Cavarretta (18-68), Harry Chiti (19-165)
PIRATES — Bobby Del Greco (19 years, 63 days on June 9, 1952)
The 19-year-old hit his first career home run in his 49th career game off the Boston Braves’ Jim Wilson. Del Greco finished his career with 42 home runs, three of which he hit for the Pirates, in 1952 and 1956.
Runners-up: Lee Walls (19-217), Dale Coogan (19-314)
REDS — Pete Schneider (19 years, 29 days on Sept. 18, 1914)
Schneider was a pitcher, but he managed five home runs in his career, including this one as a 19-year-old in 1914. He homered off the Giants’ Art Fromme, knocking an inside-the-park home run. Three of his five career home runs were inside-the-parkers. He finished his career with 16 home runs allowed.
Runners-up: Ted Tappe (19-224), Curt Flood and Vada Pinson (19-250)
D-BACKS — Justin Upton (19 years, 347 days on Aug. 7, 2007)
The only home run as a teenager of Upton’s career was this one, in his first home game and fifth overall game in 2007. He went yard off the Pirates’ Tom Gorzelanny, one of two home runs he’d hit that season. Upton and his brother, Melvin Upton Jr., each hold the record for the youngest home run for a franchise — Justin for the D-backs and Melvin for the Rays.
Runners-up: Gerardo Parra (22-7), Karim Garcia (22-153)
DODGERS — Tommy Brown (17 years, 257 days on Aug. 20, 1945)
Brown isn’t just the youngest Dodgers player to hit a home run in the Modern Era, he’s the youngest for any team in the Modern Era, as he’s the only one to go deep as a 17-year-old. Brown’s first homer came off the Pirates’ Preacher Roe. What’s even wackier than a 17-year-old homering? Brown debuted in 1944, at 16 years, 241 days old, so he could’ve done so at an even younger age, theoretically. He played in 46 games in 1944, but tallied just four extra-base hits, all doubles.
Runners-up: Adrian Beltre (19-84), Don Drysdale (20-48)
GIANTS — Mel Ott (18 years, 138 days on July 18, 1927)
Ott debuted at 17, but didn’t homer until he was 18, in his second season in the Majors. His first home run was an inside-the-parker off the Cubs’ Hal Carlson. He’d go on to hit 511 home runs in his career, which makes him one of 27 players to reach the 500-homer plateau, though when he hit No. 500, he was the first National League player to accomplish the feat.
Runners-up: Whitey Lockman (18-345), Fred Merkle (19-186)
PADRES — Roberto Alomar (20 years, 85 days on April 30, 1988)
Alomar’s first home run came off the Pirates’ Bob Kipper at Jack Murphy Stadium. Alomar hit 210 home runs in his Hall of Fame career, including 22 with the Padres. Earlier this season, Fernando Tatis Jr. became the second-youngest player to homer for the Padres, narrowly missing out on edging Alomar as he was four days older.
Runners-up: Fernando Tatis Jr. (20-89), Jerry Morales (20-204)
ROCKIES — Roberto Mejia (21 years, 100 days on July 23, 1993)
This Rockies record still stands from the team’s first year of existence in 1993. Mejia hit just 10 home runs in his career, all of them in a Rockies uniform, but he certainly hit them at a young age. The 21-year-old took Allen Watson of the Cardinals deep for his first career home run. His other four home runs in 1993 came off some pretty nifty company: Curt Schilling, Tim Wakefield, Trevor Hoffman and Tom Glavine.
Runners-up: Troy Tulowitzki (21-329), Nolan Arenado (22-13)
Sarah Langs is a reporter/editor for MLB.com based in New York. Follow her on Twitter @SlangsOnSports.