American baseball suffered racial discrimination as African American ballplayers were not allowed in MLB until Jackie Robinson broke the color barrier by playing for the Brooklyn Dodgers in 1947. Before that, in the early 1920s, Andrew “Rube” Foster, a former player, manager, and owner for the Chicago American Giants, organized African American baseball, leading to the formation of Negro Leagues.
However, many reasons can be attributed for the downfall of Negro League. The last active Negro League played was Negro American League which played its last game in 1958..
Reasons for the downfall of Negor League
#1 Integration of Major League Baseball
After the Brooklyn Dodgers signed Jackie Robinson, the path for African American players to play in the majors became easier. This resulted in a huge outflow of big names from Negro League, resulting in reduced funds and decreased popularity.
#2 Decline in attendance and revenue
When Negro Leagues first started, at times, the support often outpoured that of major league franchises. However, losing a star player to the majors and declining interest of the remaining players to play League games, resulted in the decline of attendance and revenue.
#3 Evolving social dynamics
America started to evolve in terms of racial discrimination and the amalgamation of Black and white players got normalized. The Civil Rights movement (1954-1968) also played a major role in opening doors and opportunities for athletes of color.
#4 Shift of change in fan base
Following the success of Black players in majors, the Negro League was drained in terms of fan base, as the loyal followers shifted their cheers for Major League Baseball. The Negro National League disbanded in 1948 and the Negro American League had its last game in 1958.
All in all, the combination of financial difficulties after World War II, evolving social dynamics due to Civil Right movement and MLB opening its door to Black players resulted in the decline and subsequent end of Negro Leagues.
Due to proper stats not being available all these years, MLB was not convinced to add Negro League stats to player profiles. However, in 2020, the majors decided to incorporate Negro league stats as well.