Quick answer: All Star cheer emerged from around the 1980s onward, as private gyms began forming competitive cheer teams independent of any school - a format that grew rapidly through the 1990s and 2000s and now represents a major branch of the sport.
Why All Star Cheer Emerged
As competitive cheer's technical demands grew - more advanced stunts, tumbling and choreography - dedicated gyms began forming teams built purely around training and competing, rather than combining cheer with sideline support for a school's other sports. This let athletes train year-round with a much sharper competitive focus than a typical school program allowed.
Early Growth
Through the 1980s and 1990s, All Star gyms and teams grew steadily in the United States, supported by the same competition organisations and training camps that had helped standardise cheer technique more broadly. See How Did Competitive Cheer Develop? for the wider context this growth happened within.
Standardisation
As All Star cheer expanded, the need for consistent levels, rules and safety standards across many independent gyms became clear. In December 2003, the event producers National Cheerleaders Association, Universal Cheerleaders Association, Cheersport and America's Best founded the U.S. All Star Federation (USASF) to set common rules. The first Cheerleading Worlds followed on 24 April 2004 - just 14 teams in two divisions - and the International All Star Federation (IASF) now co-hosts Worlds with the USASF and brings All Star programs from other countries into the same system. Varsity added The Summit in 2013 for teams at lower levels - see What Is All Star Cheer? for how today's level and division system works, and History of the International Cheer Union for the international federation that governs national teams.
All Star Cheer Today
All Star cheer is now a major branch of competitive cheerleading worldwide, with gyms fielding multiple teams across a wide range of levels and age groups, and a season structure built around qualifying competitions and major end-of-season championship events.
A Note on Dates
Some early details vary slightly between sources. Where sources disagree, we give the most widely cited version and avoid false precision - the sources we used are listed below.
Sources: U.S. All Star Federation (Wikipedia); The Cheerleading Worlds (Wikipedia); Varsity Spirit (Wikipedia)