Simplify the following text for a Grade 6 native English-speaking person.
Original: Keith Haring ( May 4 , 1958 â `` February 16 , 1990 ) was an artist and social activist whose work responded to the New York City street culture of the 1980s .
Simplified: Keith Haring ( May 4 , 1958 - February 16 , 1990 ) was an American artist .