Cunningham was known for his candid and street photography. He first became known as a designer of women's hats before moving on to writing about fashion for "Women's Wear Daily" and the "Chicago Tribune". He began taking candid photographs on the streets of New York City. His work came to the attention of "The New York Times" with a 1978 capture of Greta Garbo in an unguarded moment. Cunningham reported for the paper from 1978 to 2016.