The Categoría Primera A (), commonly referred to as Liga BetPlay Dimayor (between 2015 and 2019 Liga Águila) due to sponsorship by online betting company BetPlay, is a Colombian professional league for association football clubs. It is the country's premier football tournament and sits at the top of the Colombian football league system. A total of twenty clubs compete in the league's regular season. División Mayor del Fútbol Profesional Colombiano, better known as DIMAYOR, operates the league system of promotion and relegation for both Categoría Primera A and Categoría Primera B leagues. Since its foundation in 1948, fifteen teams have been crowned as Colombian football champions. The most successful club is Atlético Nacional with 17 titles. History Before 1948 there was no professional football league in Colombia. The first clubs were formed in Barranquilla and Bogotá: Barranquilla FC, Polo Club, Escuela Militar and Bartolinos, although the game took a while to develop in popularity. The 1918 Campeonato Nacional was the first tournament played between Colombian clubs, followed by the Copa Centenario Batalla de Boyacá. Independiente Medellín, founded on 15 April 1913, is the oldest club that remains as a professional club. The first tournament was organised by the Colombian Football Federation and DIMAYOR in 1948. Ten teams signed up for this first tournament, paying the required fee of 1,000 pesos). Two teams each signed on from Bogotá, Cali, Manizales, and Pereira, plus one from Barranquilla. 252 players were registered for that year's tournament, 182 of which were Colombians, 13 were Argentine, 8 Peruvian, 5 Uruguayan, 2 Chilean, 2 Ecuadorian, 1 Dominican, and 1 Spanish. Soon after the league's foundation, disputes between Adefútbol (the body governing amateur football in Colombia) and DIMAYOR (the organizing body behind the new national league) erupted. DIMAYOR broke away from Adefútbol, announcing that it would operate independently of FIFA rules and regulations. In response, FIFA sanctioned Colombian football, banning the national team and all its clubs from international competition. This period, which lasted from 1949 to 1954, is known as El Dorado. Far from being a dark time in Colombian football, this was its golden age. No longer required to pay transfer fees to clubs from other nations, Colombian clubs began importing stars from all over South America and Europe. The most aggressive signer of international players was Millonarios, which won consecutive championships with stars such as Alfredo di Stéfano. Attendances boomed, and the expanding appetite