O. Henry, born William Sydney Porter, was a renowned American short story writer best known for his surprise endings. He was born in 1862 in North Carolina and became a pharmacist at age 19, though he had begun suffering from tuberculosis. In the late 1880s, he began writing short stories in earnest to support his family while working various jobs, including as a banker and reporter. By the early 1900s, O. Henry had written over 300 short stories, nearly all with his signature twist endings. Though he faced legal troubles and imprisonment for several years, his writing popularity soared after his release, establishing him as a master of the short story form.