Complex sentence: The road then turned south to parallel railroad tracks belonging to the Great Northern Railroad and the South Fork of the Skagit River to Milltown, where SR 530 intersected Milltown Road, which would later interchange with I-5 to the east.
Split into simpler sentences: The road then turned south to parallel railroad tracks owned by the Great Northern Railroad and also parallel the South Fork of the Skagit River. At Milltown, SR 530 intersected Milltown Road, which would later interchange with I-5 to the east.