However, with older ballparks, determining what date to use for their opening is sometimes problematic. A case in point is the prior Yankee Stadium. “The House That Ruth Built” clearly opened in April 1923, but the park was closed for two seasons (1974-75) while major renovations took place. When the park reopened in 1976, the debate began as to whether this was a new park or not. The exterior shell still stood, as did some of the inside ramps, but much of the facility was new. Old-timers who fondly remembered the old configuration usually said it was a different park starting in 1976, while others looked at the still-intact shell and continued to call it a 1923 ballpark.
The situation becomes clear as mud with some ballparks that are used for minor and independent league ball. Do you use the date at which the field was first used? That would lead to declaring that Labatt Memorial Park in London, Ont., opened in 1877, when the main seating bowl was completely rebuilt in 2001 and there is no structure on site that is older than the 1950s. Yet the park was rebuilt piecemeal (the bleachers are older than 2001, though they are surely younger than 1877). In those cases, it’s sometimes easier to default to the first use of the field rather than try to tag a single date on the facility.
This is mainly a problem in the lower minors, where in some cases there has never been a permanent stadium structure. Community Park in Burlington, Iowa, has never had anything more than bleachers. I don’t know when the current bleachers were installed. As a result, I’ve listed the park with its first use for professional ball, in 1947, even though it’s not a 1947 “stadium”.
On each ballpark’s individual page, I have tried to give multiple dates when I know of significant renovations that make the park seem newer. If a new stadium is built around an existing field, I will list the old facility (for instance, they have played ball at Wahconah Park in Pittsfield, Mass., since 1892, but the current stadium was built in 1950). On the list of Current Stadiums by League, I try to list the opening date of the current stadium, using the criterion that if significant members remain from an old stadium structure, it’s a renovation, while it’s a new stadium if no members were reused (or if only ceremonial or commemorative members remain). By that standard, the original Yankee Stadium was built in 1923 and used until 2008; but Isotopes Park in Albuquerque is a 2003 facility even though it was pitched to the voters as a “renovation”, as it’s a completely new stadium built around the old field.
The following table shows the average (arithmetic mean) and median opening dates of the ballparks that are active for the 2020 season, using the dates on the Current Stadiums by League page. Compare the ballpark ages for the 2021 season.
| League | Average | Median |
| MAJOR LEAGUE BASEBALL (30 parks) | 1991.5 | 2000 |
| American League (15 parks) | 1987.4 | 1992 |
| National League (15 parks) | 1995.6 | 2003 |
| MINOR LEAGUE BASEBALL (159 parks) | 1992.22 | 1997 |
| TRIPLE-A (30 parks) | 1998.24 | 2000 |
| International League (14 parks) | 1995.57 | 1997 |
| Pacific Coast League (16 parks) | 2001.94 | 2001 |
| DOUBLE-A (30 parks) | 2001.23 | 2003 |
| Eastern League (12 parks) | 1992.42 | 1994 |
| Southern League (10 parks) | 2007 | 2004½ |
| Texas League (8 parks) | 2007.25 | 2006 |
| CLASS A ADVANCED (29 parks) | 1986.10 | 1993 |
| California League (8 parks) | 1978 | 1993½ |
| Carolina League (10 parks) | 1980.6 | 1994 |
| Florida State League (11 parks) | 1987.91 | 1991 |
| CLASS A (30 parks) | 1992.53 | 2000 |
| Midwest League (16 parks) | 1987.06 | 1995½ |
| South Atlantic League (14 parks) | 1998.79 | 2002 |
| CLASS A SHORT SEASON (22 parks) | 1988.64 | 1996½ |
| New York-Penn League (14 parks) | 1989.43 | 1998½ |
| Northwest League (8 parks) | 1987.25 | 1992 |
| ROOKIE (18 parks) | 1978.94 | 1988 |
| Appalachian League (10 parks) | 1971.6 | 1971½ |
| Pioneer League (8 parks) | 1989.25 | 2000½ |
| INDEPENDENT LEAGUES (45 parks) | 1992.68 | 2002 |
| American Association (12 parks) | 2003 | 2003 |
| Atlantic League (7 parks) | 2007.14 | 2007 |
| Frontier League (14 parks) | 1987.14 | 2001½ |
| Pecos League (12 parks) * | 1963.2 | 1949 |
| ALL PROFESSIONAL LEAGUES (234 parks) | 1992.19 | 1999 |