More specific to your question, Brad F.; the former Milwaukee Mainline from Cedar Falls to Tacoma is basically intact. Even better, you can hike/bike it from the former site of Cedar Falls, ( now Rattlesnake Lake State Park ) thru Maple Valley to Renton. From Renton to Black River Jct., the line is still in use as part of the BNSF Woodinville Subdivision. From Black River Jct. to Tacoma the line is in use as Union Pacific's mainline. You can hike/bike the Interurban Trail thru the Kent/Auburn valley, this trail basically parallels the U.P. main.