My brother, Steve wrote in his blog about the now defunct USFL which started as a Summer supplement to the NFL and then grew a little big for it's britches and finally challenged the Iconic league. It reminded me of the two upstart leagues of the 60s and 70s, the American Football League (AFL) and the American Basketball Association (ABA). The goals of both of these leagues was not nescessarily to destroy the established NFL and NBA, but to competed beside them like the American League and the older National League in Major League Baseball.
There is not much written to compare and contrast the AFL with the ABA, but there are so many similarities and yet so many differences.
The AFL no longer exists, but really it does. All of the original teams, plus the two expansion teams ( the Miami Dolphins and the Cincinnati Bengals), still exist, although the Houston Oilers are now the Tennessee Titans, the Oakland Raiders are again the Oakland Raiders, after a decade of so in Los Angeles. They exist in what became the American Football Conference (AFC). Three teams (Baltimore-Indianapolis Colts the original Cleveland Browns, now the Baltimore Ravens and the Pittsburgh Steelers), joined the AFL teams after the merger. The AFL was able to get a TV contract with NBC. It was easy for fans to watch their favorite NFL team on one channel and their favorite AFL team on the other. The AFL was established by oil baron Lamar Hunt, after the NFL stopped his bid to buy the Chicago Cardinals. Hunt owned the AFC's Dallas Texans. The Texans then moved to Kansas City and renamed themselves the "Chiefs". I think it was Hunt's money and the quality of ownership that he brought in that helped advance the AFL. Great AFL stars were Len Dawson, Joe Namath, Gino Cappeletti, and Daryl Lamonica.
Only four of the ABA teams joined the NBA. They are scattered in the league with no ties within. The ABA had no television agreement so it could not get either the exposure needed nor the money to lure the quality stars that the AFL could get. I remember an ABA all star game being played on "Wide World Of Sports" There was no common draft nor any direct competitive game with the NBA. The ABA was able to get some great stars though, Julius Erving, Connie Hawkins, and Rick Barry come to mind. It played with a Red, White, and Blue Basketball. It had the original three point line and many players had long hair and huge afro style haircuts. It was the flashier league.
The similarities are that they both brought changes to the older leagues, while the NBA does not play with Red, White, and Blue Basketballs, it adopted the "three point line" and the San Antonio Spurs (from the ABA) have won the league several times. The AFL brought the "two point conversion" , more colorful jerseys, the scoreboard keeping official gametime, player's names on jerseys, and of course the Super Bowl.
This year, the eight original AFL teams are having legacy weekends to celebrate 50 years since the founding of the league.