PONY Baseball and Softball™ began with organization of the Pony League in Washington, PA in the summer of 1951. This was a transition league for 13-year-old and 14-year-old players designed to take graduates of Little League baseball from that diamond to the regulation size diamond. Growth of Pony League, primarily by word of mouth, was rapid, and by the end of the second season, 1952, the original six teams in Washington were joined by 505 others in 106 leagues around the country. A national tournament was conducted, and the first Pony League World Series was held that year.

Lew Hays, among the founders of the Pony League, was named Commissioner of the new league when it was incorporated for national organization in early 1953 and held that post until 1964 when he was named president.

In 1953, John Laslo, long time Mayor of Martins Ferry, Ohio, visited with Hays and discussed organization of a league similar to Pony League for 15-year-old and 16-year-old players. The purpose was to permit players in this age bracket to compete with players of like experience in their first years on the regulation diamond.

Laslo guided the development of Colt League, and in late 1959, Pony League and Colt League were merged into a single organization.

Bronco League, for 11-year-old and 12-year-old players, was organized in 1961 to permit players of this age to play the complete game of baseball. With Colt League using the regulation diamond with 90 foot base paths, Pony League uses a diamond with 80 base paths as a transition between the regulation diamond and the 70 foot diamond used in Bronco League.

In 1970 the Mustang League was developed in Fort Worth, TX using a diamond with 60 foot base paths, to provide an organizational structure for leagues for beginning players, 9-and 10-year-olds. For communities using players of 7 and 8 years of age, rules and emblems were developed for Pinto League, a very elementary form of baseball.

Thorobred League was organized in the Tampa, FL area and became a part of the PONY Baseball family in 1973 to provide playing opportunity for those players from 17 through 20 years of age who have not entered professional play and who retain a desire to participate in a community baseball program.

In 1977, Thorobred League age limits were expanded to include 21-year-old age players, and Palomino League was organized for players 17 and 18. The Thorobred League was discontinued as a PONY program in 1984.

Shetland League, an instructional program for 5- and 6-year-olds, was formally adopted by PONY for the 1990 season with rules based on the experiences of a number of league organizations that had conducted play in this age group for several years.

While girls are permitted to play in any of the PONY Baseball leagues, recognizing that most girls preferred to compete in leagues with other girls, PONY Baseball provided Softball for Girls leagues in 1976. Colt League provides for girls 16-and-under and Bronco League for those 12-and-under. In communities where sufficient players are available, the Colt League may consist of players 15 and 16, and a Pony League used for those 13 and 14. Both Pony and Colt softball leagues used a regulation softball diamond with 60 foot base paths in fast pitch.

In like manner, if there are enough players, the Bronco League may be limited to players of 11 and 12 years of age and Mustang League used for those 10-and-under. These leagues for younger girls use a softball diamond with a 50 foot base path.

Older girls, 17 and 18, play in the Palomino League on the 65 foot diamond in slowpitch.

Links to: 
Pony East Zone Region Website: http://www.pony.org/East_Zone/East_Zone_Regions.htm 
Pony Rules PDF: http://www.pony.org/Assets/Corporate+Assets/Forms+and+Assets/Rulebooks/2015+PONY+Girls+Softball+Rulebook.pdf