For those who don;t have the time:
10. Hiawatha
9. Couer d'Alenes
8. Mickelson
7. Olympic Discovery
6, Katy/Rock Island
5. Palouse to Cascades
4. Northern Trail (New England)
3. Erie Canal
2. Ohio to Erie
1. GAP/C&O
I've done all of 10 and nearly all of 8 along with the GAP and the eastern 7 miles of the No. 7, which are not very interesting but quite fast as you slope down from the Bitterroots on a smooth, paved surface. Also did No. 3 from Lockport to a bit east of Rochester BITD.
I'd say the Hiawatha (and the 9 miles of right-of-way from the official end of the trail at the Pearson trail head to the town of Avery) were the most unique in terms of features and scenery. Over a dozen tunnels and several high trestles in a forested setting.
One thing that is not mentioned is that the Hiawatha continues east as the Olympian Trail where the Hiawatha ends at the East Portal trailhead. It will take you all the way to St. Regis, MT. The Bitterroot 300K, mentioned in the video, includes both the CdA trail and Hiawatha, along with other portions of the former Milwaukee Road right of way. Looks like a nice loop.
Mickelson was also a fun ride, although not as "warm and fuzzy" in the sense of cute little towns conveniently spaced. Fortunately, there are nice trail rest areas, including some with water cisterns and shelters from both sun and things like hail. Not much in the way of authorized/legal camping outside of Hill City, Custer and at the southern terminus in Edgemont. And be prepared for noticeable grades. The climb south from the Englewood trailhead is tough for a rail trail. It's worse if you start from Deadwood. And it takes you to over 6,200'.
