How does Sweet Autumn Clematis (clematis terniflora) do in your zone? A couple of those (3 max. as they can grow to 30+ feet) will cover/drape your 120' wall in pretty short order. I had a magnificent specimen in the mid-Atlantic, but it self seeded like gangbusters and became somewhat thuggish. However, with deference to a spectacular plant - the growing season there usually started in March and could go beyond Thanksgiving. Zone 5 wouldn't have the same lengthy conditions and SAC would probably be better behaved.

Then there is always Virginia Creeper (Parthenocissus Quinquefolia) which could be trained to drape. I have the creeping phlox subulata in a stone retaining wall built into a slope. It's good to soften the edges of walls, etc. but its cascading habit is somewhat limited.

Also look into sweet potato vines - annuals, but cheap at the big box garden centers. Saw some Google images of spv's used as both ground covers and trailers so there's cascading potential there too.

Have you considered evergreen Junipers, such as Blue Rug or Blue Pacific? There's many other varieties available at nurseries & more affordable @ the big box stores. I bought some Blue Rug last year for $6/pot, and they're spreading much faster than i expected, starting to cascade over a cedar retaining wall. The Blue Pacific was much more expensive, but it's beautiful!
I also put in Cotoneaster dammeri - supposedly spreads to 8', & seems tolerant of tough conditions so far. Got that small & cheap @ Home Depot.

Sweet potato vines could definately work. You see them around and they really stand out. I think I'm going to go with Clematis though.

I got all my questions answered as far as if it will work or not in another post

Here is a link that might be useful: Can clematis be used in a cascading form?