Wheelchair softball was born in the Midwest by a few individuals with spinal cord injuries and lower extremity impairments, who still wanted to enjoy America’s greatest pastime. These individuals needed to develop a way of playing without the full use of their legs that would allow easy maneuverability in a wheelchair and keep the fast pace of softball. Thus was born a new game played on hard surfaces, such as a parking lot, instead of the normal grassy infield, and a 16-inch softball, which allows wheelchair players to keep one hand one the wheelchair while catching a softball without a glove.
Taken from https://www.wheelchairsoftball.org/about