Complex sentence: Isadore Horween, who had learned the leather business in his native Ukraine, immigrated to the United States in 1893 and founded I. Horween and Co. in 1905 in Chicago, Illinois.
Split into simpler sentences: Isadore Horween, who had learned the leather business in his native Ukraine, immigrated to the United States in 1893. He founded I. Horween and Co. in 1905, in Chicago, Illinois.