The World's Oldest Continually Operating Baseball Field

May 3, 1877:

Labatt Park, the oldest continually operating baseball grounds in the world has its first game.
Labatt Memorial Park (formerly Tecumseh Park, 1877–1936) is a baseball stadium near the forks of the Thames River in central London, Ontario, Canada. It is 8.7 acres (35,000 m²) in size, has 5,200 seats and a natural grass field. From home plate to centre field the distance is 402 feet (123 m); from home plate to left and right field down the lines, it is 330 feet (100 m).
Labatt Park is the "oldest continually operating baseball grounds in the world", with a history dating back to 1877. Since December 31, 1936, the park has been owned by the City of London.
On September 7, 2011, Baseball Canada announced that historic Labatt Memorial Park in London, Ontario, had won its six-week-long, favourite ballpark contest, winning the final round where it went head-to-head with Port Arthur Stadium in Thunder Bay, Ontario. During the two-week-long, final round of online voting, where more than 19,000 votes were cast, Labatt Park won with 63 per cent of the vote.
However, Fuller Field in Clinton, Massachusetts made it into the Guinness Book of World Records in September 2007 as the "world’s oldest continuously used baseball diamond/ field", dating back to 1878—a year after Tecumseh Park-Labatt Park opened in 1877—as Fuller Field's home plate and bases have purportedly remained in the same location since 1878, whereas home plate at Labatt Park has been moved (within the same field) from its original location in 1877.
In September 2008, however, Labatt Park replaced Clinton, Massachusetts' Fuller Field in the 2009 Guinness Book of World Records (page 191) as the "World's Oldest Baseball Field." Then on October 10, 2008, Guinness's online record for the World's Oldest Baseball Field was switched back to Fuller Field in Clinton, Massachusetts. World's Oldest Baseball Field.

I didn't realize the oldest baseball field title would be so contentious.  It reminds me of the longest highway record.  It seems like the folks at Guinness have something against Ontario.