It depends on how the park is dated. A park may have been remodeled to an extent that it's considered new construction from the date or remodel, even though there are elements that are older.
Bosse Field in Evansville Indiana is the oldest minor league ballpark used full time. It was built in 1915 and is the third oldest full-time use baseball park in America behind Fenway Park and Wrigley Field.
But there's an older park used for one minor league game each season. Rickwood Field in Birmingham, AL was built in 1910. The Birmingham Barons play one game a year at Rickwood.
add on: The ballpark located on City Island, in Daytona Beach in the Halifax River, opened on June 4, 1914 as the Daytona City Island Ballpark. The current Florida State League originated in 1919. The Sanford Celeryfeds and Orlando Caps were co-champions. It served as Spring Training field for the Brooklyn Dodgers in 1915, 1916 and 1946. The St. Louis Cardinals in 1937 and the Montreal Expos 1973 thru 1980. The Ball Park was the home field of the FSL Daytona Beach Islanders (1920-24, 1936-41, 1946-66, 1977), Daytona Beach Dodgers (1968-73), Daytona Beach Astros (1978-84) and Daytona Cubs 1993 to present. On March 17, 1946, City Island Ballpark in Daytona Beach, Florida hosted more than just a baseball game. On that day, Jack Roosevelt "Jackie" Robinson played in the first integrated, professional baseball game. In honor of that monumental occasion, the City of Daytona Beach renamed the stadium Jackie Robinson Ballpark in 1990 and created the Jackie Robinson Museum within its gates.
Still standing today the two oldest stadiums in major league baseball are: Fenway Park (Boston Red Sox), and Wrigley Field (Chicago Cubs)
the oldest stadium is fenway park
Wrigley field
Fenway Park
Fenway
The oldest national park is Yellowstone National Park, established in 1872 in the United States.
Yellowstone National Park
Royal National Park
Old faithful
Fenway park I think
For the 2009 season, that is Dodger Stadium which opened in 1962. Fenway Park is oldest, opening in 1912, and Wrigley Field is second oldest, opening in 1914.
#4 - Angel Stadium of Anaheim (1966)
Fenway Park