Complex sentence: On June 20,1911, the O.C.T.C. announced that it would suspend steamboat service to points above the Willamette falls from August 1 (or late July) to October 1, because the Willamette Falls Locks would be closed for improvement works during that time.
Split into simpler sentences: On June 20,1911, the O.C.T.C. announced that it would suspend steamboat service to points above the Willamette falls from August 1 (or late July) to October 1. The reason for the suspension was that the Willamette Falls Locks would be closed for improvement works during that time.