Complex sentence: In 1914, after seven years of construction, the Northwestern Pacific Railroad completed a rail line running along much of the Eel River as an important transportation link connecting the many small towns along the Eel River valley.
Split into simpler sentences: In 1914, after seven years of construction, the Northwestern Pacific Railroad completed a rail line running along much of the Eel River. In time, it would serve as an important transportation link for the region, connecting the many small towns along the Eel River valley.