Baseball teams established in 1998

The Arizona Diamondbacks, often shortened as the D-backs, are an American professional baseball team based in Phoenix, Arizona. The Diamondbacks compete in Major League Baseball (MLB) as a member club of the National League (NL) West division. The team plays its home games at Chase Field, formerly known as Bank One Ballpark. Throughout its history, Arizona has won one World Series championship (defeating the New York Yankees in 2001) – becoming the fastest expansion team in Major League history to win a championship, which it did in only the fourth season since the franchise's inception.

The Tampa Bay Rays are an American professional baseball team based in St. Petersburg, Florida. The Rays compete in Major League Baseball (MLB) as a member of the American League (AL) East division. Since its inception, the team's home venue has been Tropicana Field.

The Fresno Grizzlies are a minor league baseball team based in Fresno, California. The team, which plays in the Pacific Coast League (PCL), is the Triple-A affiliate of the Houston Astros major league club. The Grizzlies play in Chukchansi Park (capacity 12,500), located in downtown Fresno and built in 2002. The Fresno Grizzlies' colors are black and orange. All games are broadcast on KYNO, with Doug Greenwald handling the play-by-play.

The Memphis Redbirds are the Triple-A minor league baseball affiliate of the St. Louis Cardinals. They play their home games at AutoZone Park in downtown Memphis, Tennessee. The stadium's capacity is 10,000. They entered the Pacific Coast League (PCL) as an expansion team in 1998, and were owned as a non-profit community entity until being acquired by the Cardinals organization in November 2013. The Redbirds had been previously operated by Global Spectrum, a Comcast-owned company. The purchase was completed on March 24, 2014.

The Somerset Patriots are an American professional baseball team based in Bridgewater Township, New Jersey. They are a member of the Liberty Division of the Atlantic League of Professional Baseball, which is not affiliated with Major League Baseball. From the 1999 season to the present, the Patriots have played their home games at TD Bank Ballpark.

The Huntington Rail Kings were an independent professional baseball team based in Huntington, West Virginia during the 1998 season. The Rail Kings played in the Heartland League and played their home games in St. Cloud Commons. The team was the third and final professional baseball team to be based in Huntington during the 1990s, after the Huntington Cubs (1991-1994) and the River City Rumblers (1995). The franchise relocated to Huntington from Altoona, PA where they were known as the Altoona Rail Kings.

The Springfield/Ozark Mountain Ducks were a minor league team that previously played in Ozark, Missouri, a suburb of Springfield. The team was a member of the Texas-Louisiana League, later named the Central Baseball League from 1998 to 2003. The team played in Price Cutter Park.

The Bethesda Big Train is a collegiate summer baseball team based in Bethesda, Maryland. Most of its players are drawn from the college ranks. The team is a member of the Cal Ripken Collegiate Baseball League (CRCBL), and derives its name from the nickname of Hall of Fame pitcher Walter Johnson, who was a Bethesda resident for ten years. The Big Train plays its home games at Shirley Povich Field. The Big Train is owned and operated by the non-profit The Bethesda Community Base Ball Club, Inc., and is funded through merchandise sales, donations, and other fundraising efforts at games. As of March 2008, 34 Big Train Alumni have played professional baseball.

The Newport Gulls are a wooden-bat, summer collegiate baseball team based in Newport, Rhode Island. The Newport Gulls Baseball Club is a member of both the New England Collegiate Baseball League and the NECBL's Southern Division. From 2001 to the present, the Gulls have played at Cardines Field.

The Long Island Ducks are an American professional baseball team based in Central Islip, New York. They are a member of the Liberty Division of the Atlantic League of Professional Baseball, which is not affiliated with Major League Baseball. Since the 2000 season, the Ducks have played their home games at Bethpage Ballpark - formerly known as EAB Park, Citibank Park, and Suffolk County Sports Park.