With the 15-inch mound a constant, good hitters hit, good pitchers thrived, and the pastime thrummed along through three wars, a cruel Great Depression, and crowned its World Series champions.
So why did the Lords of Baseball decide in a fit of panic after a 1968 season known as "The Year of the Pitcher" that after 65 years of baseball's rhythmic swings they needed to lower the mounds by 26.6 percent to 11 inches?
It's an easy answer when the third-most radical rule change of the 20th century - behind creation of the designated hitter and the ban of the spitball - is viewed through the prism of 40 years.
The mound was lowered in an attempt to restore competitive balance to a game where the once-mighty AL had become decidedly inferior to the National.
How and why? Well, let's take a look at that so-called "Year of the Pitcher":
* Five American League pitchers - Luis Tiant, Dave McNally, Sam McDowell, Denny McLain and Tommy John - had ERAs under 2.00. None is in the Hall of Fame.
Now, let's check the hitters they faced that season:
Carl Yastrzemski led the AL with a .301 batting average. At No. 10 at .274 was Rick Monday. Only Yaz is a Hall of Famer.
Now let's check the National League:
Pete Rose won the batting title at .335; Roberto Clemente was 10th at .291. The NL produced below-average but not anomalous offense in a season when Bob Gibson's ERA was a modern-era record 1.12. Willie McCovey led the NL with 36 homers.
But the most telling numbers in the power stats were these: Six of the top 10 NL home-run leaders that year went to the Hall of Fame; all six were players of color. Just two of the top 10 AL home-run leaders, Yaz and Reggie Jackson, are HOF members. Just two, Willie Horton and Jackson, were players of color. Therein lies the real story.
By the late 1960s, the integration of African-Americans and Hispanics into MLB had become imbalanced. The National League had more talent and diversity, pure and simple. A rare confluence of peaking pitchers had driven the AL's offensive wing to its knees. But it had damn little to do with a mound that was the same height in 1961, when Norm Cash hit .361, Roger Maris hit 61 homers and six AL sluggers hit more than 40 bombs.
Same damn 15 inches . . .
The Lords of Baseball wanted to restore offensive balance. That's what they said at the winter meetings. What they didn't mention was that they really wanted to prop up the AL.
And, wow, look how it worked. In 1969, five AL sluggers, led by Harmon Killebrew's 49, hit more than 40 homers. Offense was up in both leagues. What the Lords didn't say was that the diluted pitching supplied by expansion teams in Seattle, Kansas City (replacing the A's' carpetbag move to Oakland), Montreal and San Diego might have had as much effect as the lowered mounds.
http://www.philly.com/philly/sports/20090812_Bill_Conlin__MLB_should_raise_the_mounds_and_lower_the_ERAs.html 
