You see, Costa Rica, El Salvador, Guatemala, Honduras, and Nicaragua all gained their independence that day. Meanwhile, Mexico celebrates its independence day on Sept. 16, followed by Chile’s independence day on Sep. 18.

Furthermore, another benefit of Hispanic Heritage Month spanning between two months is that it encompasses Columbus Day or Día de la Raza, which falls on Oct. 12. Día de la Raza or “Race Day” is celebrated every year to recognize the cultural fusion of indigenous America and Spanish heritage.

Source: https://www.distractify.com/p/why-does-hispanic-heritage-month-start-on-september-15th