Complex sentence: In 1900, he started a banking and investment firm named G.H. Walker and Co. His family had developed many international banking contacts, and he helped organize the 1904 St. Louis World's Fair.
Split into simpler sentences: In 1900, he started a banking and investment firm named the GH Walker and Company. Walker's family had developed many international banking contacts and he helped organize the 1904 St. Louis World's Fair.