Roads on ledges

[Max Rockatansky]

More stuff from California:

-  Nacimiento-Fergusson Road in Big Sur
-  Santa Rosa Creek Road (old CA 41/46) descending "The Wall."
-  Old Creek Road south of CA 46
-  Sierra National Forest Route 81/Minarets Road
-  Italian Bar Road
-  Million Dollar Road
-  CA 49 Merced River Canyon
-  Wawona Road Yosemite National Park
-  Big Oak Flat Road south of Tioga Road
-  Hetch Hetchy Road
-  CA 193 Georgetown Divide
-  Mosquito Road approaching the Mosquito Bridge
-  CA 35/Skyline Drive
-  CA 130/Mount Hamilton Highway
-  CA 175 east of Old Hopland to CA 29
-  Much or CA 70 on the Feather River Highway
-  Coastal Drive (Old US 101) Prairie Creek Redwoods State Park
-  Conzelman Road Marin Headlands
-  Panoramic Highway
-  Muir Woods Road
-  Tunnel Road in Oakland
-  San Juan Canyon/County G1
-  The dirt part of Pozo Road (Old CA 178)
-  Los Angeles County N2 which incorporates part of Old Ridge Route and Pine Canyon Road
-  CA 4 east of Bear Valley towards Ebbetts Pass
-  CA 108 climbing east to Sonora Pass
-  Parts of Tulare County Mountain Road 56, 99 and 107
-  North Fork Road (old Colony Mill Road) north of Three Rivers.
-  Dunlap Road/Old CA 180
-  Sand Creek Road approaching Dunlap Road
-  Dinkey Creek Road at the Wishon Reservoir
-  Burma Grade Road
-  Donner Pass Road/Old US 40
-  Carquinez Scenic Drive/Old US 40
-  Parts of CA 128 east of Napa Valley

[skluth]

There's some quite busy ones in So Cal.

CA 74 west of Lake Elsinore
CA 74 again south of Palm Desert (best known for the opening scene of It's a Mad Mad Mad Mad World)
San Diego County Road S22 west of Borrega Springs
CA 243 entering Idyllwild
I've driven all these. Most of the bigger climbs into the mountains - Idyllwild, Big Bear, and the San Gabriel Mountains - have a few scary cliffs on one side of the road at some point. And that doesn't even count driving to Big Sur on CA 1.

Some others off the top of my head in the SoCal Area:

-  Dirt CA 173 (which isn't open to traffic but nonetheless is on a ledge).
-  CA 39 south of CA 2/Islip Saddle
-  Angeles Forest Highway
-  CA 2 Angeles Crest
-  CA 23 in Decker Canyon and Grimes Canyon
-  CA 33 Maricopa Highway
-  Hudson Ranch Road
-  Caliente-Bodfish Road
-  Woodland-Tehachapi Road (Old US 466)
-  CA 154 east of San Marcos Pass and nearby Old CA 150 on Stagecoach Road
-  Cat Canyon Road
-  Mulholland Highway (mostly the dirt segment)
-  CA 58 west from Maricopa towards Soda Lake
-  CA 178 Kern Canyon

Max has driven far more of these than I will ever attempt. If you're looking for anything in California, he's probably the first one to ask. I hadn't thought about Mulholland Drive, but even the tour bus segment looks down some cliffs.

[Max Rockatansky]

^^^

I'm starting to realize I've had way too much time on my hands over the years with all these ledge side drives.  I kind of prefer Dirt Mulholland given there aren't any houses and you get a really good idea how high the road is atop the Santa Monica Mountains.  Too bad the dirt segment requires use of a mountain bike given its is now banned to cars. 

A couple more California:

-  Parkfield Grade Road/Parkfield-Coalinga Road south of Coalinga.
-  CA 198 west of Old Lewis Creek Road (Old CA 25) west to CA 25 (hell of a view of the San Andreas Fault).
-  Some of the hairpin segments of Coalinga Road in San Benito County. 
-  Panoche Road/County J1 east of Panoche Pass over the Jackass Grade
-  San Juan Grade/Salinas Road (a Ridge Route like segment of Old US 101)
-  Old Stage Road south of San Juan Bautista
-  CA 9 Waterman Gap
-  CA 49 north of Cool to Auburn. 
-  CA 162 approaching the Bidwell Bar Bridge
-  CA 263/Old US 99 Shasta River Canyon
-  Stage Coach Road Cuesta Pass
-  Sierra National Forest Route 10/Sky Ranch Road ascending above Oakhurst
-  A large segment of Ben Hur Road south of Mariposa
-  Much of Old Highway south of Mariposa
-  The top of Yokohl Valley Drive
-  Bald Hills Road in Redwood National Park
-  Eastern CA 169
-  La Gloria/Gloria Road north of Pinnacles National Park
-  CA 190 west of Towne Pass to Panamint Valley
-  CA 172 Mineral Summit

[FrCorySticha]

Going-to-the-Sun Road in Glacier was mentioned earlier, but another road in Montana and Wyoming that fits is US 212 over Beartooth Pass. Like GttS, this is a seasonal road that is well worth the time to drive when it's open.

[roadman65]

NY 218 on the Storm King Highway in Orange County, NY between West Point and Cornwall is one.  Overlooking the Hudson below it and upward is the big hill the road is named for.

[MCRoads]

Skyline Drive in Cañon City, CO

Several keep trails in Moab, UT are right along edges.

And, probably one of the most famous: Pikes Peak Highway is almost entirely on the edge of a cliff for most of the upper portion.

[SSR_317]

Some Arizona:

...

The dirt part of AZ 88 east to Tortilla Flat.

...

I know you meant to say "east from Tortilla Flat to Roosevelt Dam", Max. But yeah, the Fish Creek Canyon section is unnerving, but spectacular. Especially when you're headed east (downhill) and some local comes roaring uphill in a huge RV towing a boat!