Guessed it right, hwy61 into Davenport.  When you think about getting upwards to 20,000 bicycles thru Davenport to the river that is pretty much the easiest route.  Easiest and safest while definite not the most scenic.  And they have blocked off lanes on 4 lane highways before so it can work.  And just think of that nice downhill coming into to town after stopping at Blueport Junction for a brew.