Complex sentence: Before Interstate 80 was built U.S. Route 206 ran on Route 183's current alignment, and therefore the circle was a major intersection of two heavily travelled U.S. Routes.
Split into simpler sentences: Before Interstate 80 was built andU.S. Route 206 was moved to its new bypass and onto Interstate 80 itself, it ran on Route 183's current alignment. Therefore the circle was a major intersection of two heavily travelled U.S. Routes.