Complex sentence: With the onset of the Great Depression, Rowland was laid off from Smith, Hinchman & Grylls so formed his own office where his work decreased to a small number of churches, schools, and construction projects.
Split into simpler sentences: With the onset of the Great Depression, Rowland was laid off from Smith, Hinchman & Grylls. As a result he formed his own office where his work decreased to a small number of churches, schools and construction projects.