"National Hispanic Heritage Month celebrates and recognizes the contributions Hispanic Americans have made to American society and culture and honors five of our Central American neighbors who celebrate their independence in September."
-Library of Congress webpage
"The timing is key. Hispanic Heritage Month... always starts on September 15, a historically significant day that marks the anniversary of independence of five Latin American countries: Costa Rica, El Salvador, Guatemala, Honduras and Nicaragua. The designated period is also a nod to those from Mexico and Chile, which celebrate their independence on Sept. 16 and Sept. 18, respectively."
From the US Census Website - https://www.census.gov/newsroom/facts-for-features/2020/hispanic-heritage-month.html