Estimating the length of long home runs is usually a flaky business, rife with ignorance, partisanship, exaggeration, and emotion. We wouldn’t offer such shoddy goods here. What follows is based on measurement of the architects’ drawings of the original 1923 Yankee Stadium and 1936 right-field grandstand extension, some knowledge of the structural changes wrought by the 1974-75 overhaul, and research help from Ken Shouler and David Gratt.
The pre-1974 upper deck had 24 seating rows and a roof that extended forward to the first row of seats, but the remodeling removed the roof, added 10 rows in back, and provided a small “sunscreen” rather than a full roof. It was theoretically possible to hit a ball onto the old right-field roof, but today’s is well out of reach.
Mantle’s 1963 homer has been stated as traveling either 367 feet or 374 feet before slamming into the roof facing, but the distance was more like 351 feet. The ball was about 108 feet high at impact. Bonds’s blow was caught at a height of about 85 feet (24 feet below the old roof), at a point about 41 feet beyond the roof facing. Given the high trajectory of long home runs, this ball wouldn’t have reached the seats in the old park—the roof would have intercepted it, 10 or 20 feet back from the lip.
The Yankees’ estimate of 620 feet for Mantle’s shot was, of course, a shameless PR ploy. Unimpeded, the ball would have hit the ground well short of 500 feet. And probably so would have Bonds’s. The Yankees’ 385-foot guesstimate for the distance that Bonds’s homer actually traveled is reasonable—we measure it as 380 feet. What’s unreasonable is to let that low number stand as though it were informative. The official Major League Baseball measurement system, originally designed by IBM, was meant to predict the field-level landing point of the ball, not where it happens to hit the structure or a fan’s hands. But MLB never really enforced the system, and what we now have is a hodgepodge of local practices.
The distances that Mantle’s and Bonds’s blasts would have gone may be similar, but there’s a significant difference—Mantle’s fell short of the roof, and thus stayed in the park. But because Bonds’s was hit closer to the foul line, it would have cleared the roof facing and become the first and only game ball to leave the stadium.