Pete Alonso has set the single-season mark for home runs by a Major League rookie and by a Met, regardless of tenure, and he led both the National League and the Majors in 2019. It’s time to dig into what that means -- leading the Majors in homers as a rookie.

Here’s a hint: It hasn’t happened much.

There have been just six rookies to lead their league in home runs in a season -- all have been outright, no rookie has tied for his league’s lead. Alonso became the first rookie to lead the Majors outright in home runs.

Here’s a look at the six rookies to lead their league in home runs.

Pete Alonso (2019 NYM): 53 HR, led MLB

No rookie had ever led his league in home runs outright before 2019, but that all changed when Alonso stepped to the plate. First he broke the Mets' rookie record, then later the Mets' single-season record and others throughout the year. On Sept. 28, Alonso hit a 2-1 pitch from Mike Foltynewicz to deep right-center field at Citi Field for his 53rd of the year, breaking a tie with Aaron Judge for the most homers by a rookie in a single season. That doubled as the Major League lead, making him the first to lead the Majors outright in homers, after two previous rookies had tied for the Major League lead.

Aaron Judge (2017 NYY): 52 HR, led AL

After a 27-game cup of coffee in 2016, Judge’s rookie season in 2017 couldn’t have gone much better. He won the American League Rookie of the Year Award, finished second in the MVP voting and was an All-Star as well as winning a Silver Slugger Award. He hit 52 homers to lead the AL. But his future teammate Giancarlo Stanton hit 59 for the Marlins, meaning Judge did not lead the Majors. But he didn’t just lead the AL, he led it handily -- with Khris Davis finishing second in the league with 43 home runs.

Mark McGwire (1987 OAK): 49 HR, led AL & tied for MLB lead

McGwire’s 49 homers in 1987 stood as the Major League rookie record until Judge came along in 2017. McGwire won AL Rookie of the Year honors, was an All-Star and got MVP votes, too. His 49 home runs were the most in the AL and tied for most in the Majors with the Cubs’ Andre Dawson. McGwire led the AL by two homers, edging out George Bell’s 47 for the Blue Jays.

Ralph Kiner (1946 PIT): 23 HR, led NL

The 23-year-old debuted in April and hit the ground running, racking up 23 homers to tie the Pirates’ single-season record at the time. That total led the NL by one -- just ahead of Johnny Mize’s 22 for the Giants. Kiner and Mize were the only two 20-homer hitters in the Senior Circuit in 1946. However, Kiner did not lead the Majors thanks to Hank Greenberg’s 44 for the Tigers that season. In total, there were five AL players with more than 23 homers that year: Greenberg, Ted Williams, Charlie Keller, Pat Seerey and Joe DiMaggio.

Tim Jordan (1906 BRO): 12 HR, led NL & tied for MLB lead

Jordan played eight games in 1901 and 1903 combined, but was still a rookie in 1906 when he hit a whopping 12 home runs for the Dodgers (then known as the Superbas). He was the only National Leaguer to reach double digits that year, and led the NL by three over teammate Harry Lumley, who hit nine home runs for Brooklyn. He tied for the Major League lead with the Athletics’ Harry Davis.

Harry Lumley (1904 BRO): 9 HR, led NL

Lumley led the National League in both homers and triples in 1904, after joining the Majors following time with the American Association and Pacific Coast League prior. A 1907 account said that “Some of the veteran fans hold him to be the best slugger in the history of baseball.” In 1904, he had a two-homer lead over anyone else in the NL with his nine, but did not lead the Majors thanks to Davis, noted above, who hit 10 for the Athletics to lead the AL and the Majors.