That honor goes to Rickwood Field in Birmingham, Alabama. It was built in 1910, and over the years it hosted teams from the multiple minor leagues, the Negro Southern and Negro National Leagues, and Major League Baseball spring training. It still hosts occasional games today, most notably the annual Rickwood Classic.

The oldest ballpark in the MLB, of course, is Boston’s Fenway Park, which was built in 1912. Chicago’s Wrigley Field, built in 1914, is the only other MLB stadium in the 100+ years club.

Icons of the game have issued numerous prodigious blasts worthy of awe, but the actual distance is apocryphal and subject to much hyperbole. Examples include:

Mickey Mantle - 660 Feet

• Mickey Mantle - 634 feet. On 4/15/1961, Cincinnati Reds outfielder Wally Post hit a shot in St. Louis that traveled 569 feet. In the news article from the Cincinnati papers, Stan Musial was quoted it was by far the longest homer he ever witnessed. Bob Nieman, a Cardinals out fielder who also witnessed Mantle's famed shot in Washington stated this was longer than Mantle's.
• The Mick hit the first taped home run at 660ft at Griffth stadium after he hit the roof five times coming within mere feet of hitting it out of Yankee Stadium. "ON ONE LEG." Micky Mantle FOR THE YANKEES hit a ball 660 feet. the real record.
• Mickey Mantle at Yankee Stadium on 2-3 occasions hit 550-560' and one occasion 570'-620'. Mick has the record. In an exhibition game, Mickey Mantle hit a ball 660 feet. He was also known for hitting home run's over 600 feet on more than one occasion.
• Mickey Mantle hit a 643-foot homer according to the Guinness Book of World Records.

• Babe Ruth 601' at Navin Field in 1941, plus about 6-8 other occasions 550'--600' possibly a bit more.
• I was told watching a Boston Red Sox game (seeing I'm from Boston) of two longest distances for home runs, not only in Fenway Park, but ever. In Fenway Park, there is a single red seat in the center field bleachers Section 42, Row 37, Seat 21, that measures 502 feet from home plate. Ted Williams (Teddy Ballgame) hit a home run off of Fred Hitchinson off of the Detroit Tigers June 9, 1946, the furthest home run in Fenway Park history. The other home run was also hit by Ted Williams and measured a distance of 565 feet from home plate.
• Manny hit a 500-510 homer.
• Adam Dunn hit a 595 footer off Jose Limas at Great American Ballpark in Cincinnati.
• Alex Rodriguez hit a ball about 535' in July 05.
• Ralph Kiner 560' at Forbes Field.
• Frank Howard 560' at Forbes Field.
• Jimmie Foxx 550' at Shibe Park.
• Ted Williams 613'.
• The longest one in recent history was Big Mac's 545 ft steroidal shot off the facing of the center field upper deck at Busch Stadium in St. Louis. That was a conservative estimate too. They have a band aid on the spot. That was in 1998 off of Ramon or Dennis Martinez (both gave up a 500+ shot off to him that year, so it's one or the other). The one Mac hit off the back wall ABOVE the upper deck at the King Dome a year earlier off the Unit was measured at 538ft (again, conservative). He's hit several like that.
• Was Andreas Galaragas "Five mile Home run" at Joe Robbie/Pro Player stadium ever measured? The one he hit into the upper deck of left field while he was still playing for the Colorado Rockies?
• Most of your questions should be answered if you go to this link. www.baseball-almanac.com/feats/art_hr.shtml
• Ernie Lombardi of the Cincinnati Reds in 1931.
• The person to hit the longest home run is Roger Connor.
• Josh Gibson's Legendary Blast. There's a famous story that Josh Gibson hit a ball that disappeared out of the park in Pittsburgh and was ruled a home run. The next day in Philadelphia a ball fell from the sky and a stunned outfielder reacted and caught it. The umpire immediately pointed to Josh Gibson and shouted "You're out in Pittsburgh, yesterday." This blast unfortunately doesn't count as a potential longest home run in MLB, because (in addition to being an even greater exaggeration than most of the other candidates) it occurred in the Negro Leagues, not in the MLB.
• As is proper in a sport where arguing about feats and comparing cross-generational exploits is part of the fun, there is no real answer. An interesting article about how home runs are accurately (rather, inaccurately) measured: http://www.baseball-almanac.com/feats/art_hr.shtml. The definitive article about the (probable) actual distances and researched reality of prodigious home run distances may be "Long Distance Home Runs," William J. Jenkinson's 1996 article in The Home Run Encyclopedia. Essentially, anything over 450 feet is truly remarkable, and few ever reach the 500 foot mark, which is truly exceptional.
• Dave Kingman's April 14, 1976 blast at Wrigley Field actually hit the third house beyond Waveland Avenue, 530 feet away. All others are subject to debate as where they might have landed, were measured where found so they had rolled some distance, whether the ball was rising or falling at the time it hit some portion of the stadium, velocity, and various other factors.
• I heard that Babe Ruth hit a home run in Fort Wayne Indiana and it landed in a train car while the train was moving. It kept on going.
• The farthest collegiate homerun was in 2008 at Irwin Field in Tyler, Texas by UT Dallas leftfielder Jared Smith.

This is from Tim McCarver, so take it with that in mind, but he said that it was born from a comment that an announcer made early on. He said "They look like bulls waiting to be let out of a pen," referring to the relief pitchers.

More input from WikiAnswers Contributors:

• Apparently it is because a long time ago, they used bulls for entertainment and they kept them there.
• The game was played out in the fenced in areas of fields where the cows and bulls ate the grass making it the ideal place to play ball. Off to the sides was a very much smaller fenced-in area where the bulls where kept when the farmers didn't want the bulls grazing. This is where other pitchers warmed-up ... out of the field of play.
• Bull Durham tobacco used to be advertised in baseball stadiums, notably in and around (a) the outfield fence and, as a particular subset of (a), (b) the area where pitchers would warm up. That's the brief, vague-ish version, but it's essentially the correct one.
• "Bullpen" has nothing whatsoever to do with actual bulls.
• Etymology (i.e. genealogy for words) is a notoriously inexact science.The most common explanation for the origin of the term "bull pen" seems to be that Bull Durham chewing tobacco was advertised in that area of the field.
• I have heard the term came from old small Midwest ball-fields built on farms and near old small western rodeo arenas. They used the old pens where the bulls were kept for the relief pitchers to warm up in, i. e. the "Bullpen".
• It is called a bull pen because in the early day's they had baseball fields and farms and the pitcher would warm up in the same pin as a bull. This would get there adrenalin going and get the pitcher ready.

While organ music had appeared at hockey rinks in the 1930s, it first bellowed through a baseball stadium on April 26, 1941. Organist Ray Nelson played “classic and soulful compositions” before the Cubs took on the Cardinals at Wrigley Field. He had to stop before the game started, however, because he was playing copyrighted songs that could’ve been picked up by radio broadcasts.

The baseball-stadium organ caught on quickly, however; the following season, the Brooklyn Dodgers hired a permanent organist, and their popularity increased through the mid-20th century. Nowadays, they’re commonplace.

Oddly enough, the Cubs removed Nelson’s organ from the grandstand during a road trip shortly after it first appeared—the copyright liability was just too much for them—and organ music wouldn’t return to Wrigley until 1967.