Charles Rudolph Walgreen (October 9, 1873 – December 11, 1939) was a United States drugstore businessman. He was born in Galesburg, Illinois (which is in Knox County), the son of Swedish emigrants, on October 9, 1873.
As a young adult, he lost part of a finger in an accident at a shoe factory. The doctor who treated him persuaded him to become an apprentice for a local druggist. In 1893, Walgreen went to Chicago and became a registered pharmacist.
At the start of the Spanish-American War, Walgreen enlisted with the 1st Illinois Volunteer Cavalry. While serving in Cuba, he contracted malaria and yellow fever, which continued to plague him for the rest of his life.