DENVER — The last time Coors Field hosted the MLB All-Star Game was in 1998.
The American League beat the National League 13-18, and it remains the highest scoring All Star game in MLB history.
And there's a reason why that is the case: the dry and thin air.
Because Denver is a mile above sea level, the air is thinner, which means there's less resistance. Denver has about 15% less air resistance than a city at sea level — that means fewer molecules for that baseball to go through. Up in Leadville, it'd be 25% less resistance, though you'd be breathing harder as you ran across the bases.
It's the same reason why at Empower Field at Mile High the field goal kickers can kick the ball farther — less air resistance.
The other part of the equation is that Colorado has drier air.
What that means is the baseball tends to be dried out a bit more, so the surface of the ball and the strings on it don't swell as much as they would in a humid area, like St. Louis or Houston.
That means that as the ball goes through the air, the off-speed stuff doesn't have enough to grab on to, making it less effective. The fastball is faster, but curveballs and off-speed pitches don't work as well.
It's tougher for the pitchers to throw effective stuff to the hitters, and that's the reason why we get more home runs and a lot more offense in Colorado.