[Princeps-Hispanico]

Several big American sports originated shortly after WW2 (NBA and NASCAR for example) and the NABL (later known as USBL for a period of time) was one of them. The idea came from several rich businessmen in the New England area. They had to think about how they could they create a baseball league that rivals the MLB. This was hard, because the MLB was already a well established sport with well established teams and the other league that challenged it (Federal League) collapsed within a few years, but they came up with some ideas. Open up teams in some markets that MLB teams hadn't expanded to. They even put teams in small markets like El Paso. The reason? The population was growing. The NABL was forming and by early 1948 the stadiums were ready and all the teams commenced play.
A chunk of the players from independent leagues and backup players from the MLB joined and were a part of the inaugural draft, and in the coming years players from colleges started showing up in the NABL draft instead of the MLB. Now you may be thinking, "Why would any college player want to play for a not as established league like the NABL?" A ton of them set out to the NABL because of being pioneers in a new sport, not to mention the fact that the NABL was more innovative than the MLB. It was also more welcoming sport with a ton of international players choosing to play in the NABL. The things the NABL tried to do to set it's self apart from the MLB was have more vibrant jerseys, have exciting things such as introducing the home run derby in 1953 (Introduced in the MLB in 1985) and the prospects game to showcase future talents. Double A and Triple A teams were also formed from some teams in the independent leagues. A few years into the future when players were coming out of colleges and started filling up the league with some notable players like Matt Garland, Lex Schuurman, Cody Moring, Josh Jacobs, and Dave White to name a few. The NABL had already lasted longer than the Federal League by 1951. While the MLB tried to run the NABL out of business the NABL held on... by a thread. Some teams had started to go bankrupt by 1950 and it was hard competing with the MLB. Turns out at this point more people were interested in going to MLB baseball games than going to NABL baseball games. The MLB had the most popular players in the country, players like Phil Petrozza, Dennis Samuels, Brian Roitman, and Jose Duran couldn't compete in terms of popularity as the MLB players such as Stan Musial, Jackie Robinson, Ted Williams, Yogi Berra... You get the point. All these players who couldn't get their footing in the MLB weren't as popular as the ones who could. When the league almost went bankrupt in 1950 companies in the cities these teams were in started funding some teams and attendance slightly increased so it guaranteed the life of the league for at least a few more years.
TL;DR Rich People create a baseball league.

Anyway let's jump into the leagues history.