Before Bryce Harper added his name to the Major League registry in 2012, there had been only 35 players who played in at least 450 games through the conclusion of their respective age-22 season. As ranked by OPS+, the top four on that list of 35 don't need much of an introduction. They are Ty Cobb (163 OPS+), Jimmie Foxx (159), Mickey Mantle (148) and Mel Ott (147).
With Harper completing his fourth season in 2015, that pre-2012 list of 35 has expanded, and that legendary quartet is now bookended by two active players: the sparkling Mike Trout (who has surpassed Cobb and leads with his blazing 167 OPS+) and Harper and his 143 OPS+.
It has sometimes been easy for Harper to get overshadowed by Trout, but Harper has carved a path previously marked by some of the game's goliaths. For example, through age-22:
• Harper ranks seventh in home runs, behind Hall of Famers Ott, Eddie Mathews and Frank Robinson, contemporaries Alex Rodriguez and Trout, and fellow teenage phenom Tony Conigliaro.
• Harper stands in a tie with Hall of Famer Al Kaline for the ninth most extra-base hits. Those ahead: Ott, Rodriguez, Hall of Famer Ted Williams, Trout, Hall of Famer Ken Griffey, Jr., Cesar Cedeno, Foxx and Vada Pinson. Perhaps most impressive is the fact that Harper's stats through the age of 22 match up quite nicely with those of Mickey Mantle, who is considered one of the most dynamic stars in MLB history. Imagine that: Mantle and Harper side by side. But we can do more than imagine.

Now, as for single-season accomplishments:
• Through his age-22 season, Mantle's single-season highs included 67 extra-base hits (in 1952), 37 doubles (1952), 27 homers (1954), 291 total bases (1952), a .311 average (1952), a .408 OBP (1954), a .530 slugging mark (1952), a .933 OPS (1954) and a 162 OPS+ (1952);
• Through his age-22 season, Harper's single-season apexes (all coming in 2015): 81 extra-base hits, 38 two-base hits, 42 homers, 338 total bases, and his .330/.460/.649/1.109, 195 OPS+ line.
And this is where Harper has a notable edge on Mantle: Through age 22, Harper's season high for wins above replacement is 9.9, which he accomplished in 2015 en route to winning the National League MVP Award and MLB Player of the Year. Mantle's high was 6.9, which also came at the age of 22 in 1954.
Mantle's 1955 season saw the Yankees' center fielder soar even higher than before. It started a 10-year run in which he would claim three American League MVP Awards and one AL Triple Crown, average 37 homers and 109 walks per season, and assemble a .314/.443/.614/1.057 slash line (188 OPS+).
Squint, and Mantle's 10-year destruction of the AL from 1955-64 looks like what Harper did in 2015. Last year, Harper looked an awful like Mantle at his (extended) peak. Let's hope the Nationals' outfielder has similar types of history-making days in his plans.