Simplify the following text for a Grade 4 native English-speaking person.
Original: In the United States , Patriot Day occurs on September 11 of each year , designated in memory of the 2,977 killed in the September 11 , 2001 attacks .
Simplified: It happens on September 11 of each year . It remembers the 2,977 killed in the September 11 , 2001 attacks .