Baseball has been proudly coined “the national pastime” for nearly its entire existence. The sport evolved from several English bat and ball games and quickly became part of the American identity in the 19th century. Only a few decades after the first baseball club formed in New York City, amateur clubs began to organize into loose confederations as competition and glory entered a game originally associated with fraternal leisure. Soon after, clubs with enough fans and capital began to pay players for their services and by 1871 and league of solely professionals emerged. Known as The National Professional Base Ball Players Association, this league would only last five seasons but would lay the groundwork for the American tradition of professional sports that exists today. In this paper, I analyze the development of the sport of baseball into a professional industry alongside the concurrent industrialization and urbanization of the United States. I used primary documents from the era describing the growing popularity of the sport as well as modern historians’ accounts of early baseball. In addition, I rely on sources focusing on the changing American identity during this period known as The Gilded Age, which many attribute to be the beginnings of the modern understanding of American values. Ultimately, I conclude that baseball’s progression into a professional league from grassroots origins compared to a broader trend of the ideal American being viewed as urban, skilled, and affluent despite the majority not able to fit this characterization. How certain attributes become inherent to a group identity and the types of individuals able to communicate these messages are also explored. My analysis of the National Association of Professional Base Ball Players provides insight on the formative experience of the modern collective American identity and baseball’s place in it as our national pastime.