Abstract expressionism was an influential art movement that began in the 1940s in New York City. It focused on spontaneous, abstract paintings that expressed the artist's inner feelings rather than representing external scenes or objects. Key artists included Jackson Pollock, known for his "drip" technique, Willem de Kooning, a leader in the 1950s, and Franz Kline, who created black and white paintings resembling Japanese calligraphy that influenced modern architecture. The movement emphasized personal expression over social messages and was influenced by surrealism and earlier abstract artists like Kandinsky.