There is a a possibility that a compacted base will move which is not what you want with a mortared wall especially one with a veneered face.

Keep in mind a wall retainer wall or not is anchored into the footing via re bar rods.

Good Day ...

A poured concrete footing below the frost line is what is necessary. In a zone 5 it is probably at least 48" below grade.

This is an easy one. You need a footing for the same reason that people need feet. Even when I'm standing on solid ground with no one pushing me from the behind or the front, I seem to have a remarkable need for my feet. You need a footing because a solidly connected wall (like I'm connected to my feet) will move differently than a boulder wall where there a breaks or a landscape block wall that leans back into the hillside exerting weight and pressure backward to counteract the forces pushing it forward.

Going back to the feet analogy, the wall is like you playing a game of tug-of-war. If you stand perfectly upright, it really doesn't take much forward motion to pull you over. If you could not bend at the knee or take a step forward, you'd simply fall. If you were standing there but didn't have feet at all- no chance. A landscape block wall leans back- as you would- exerting opposite pressure which makes it harder (though not impossible) to pull forward. That they are not mortared together enables them to move slightly with the ground and absorb the kinds of 'shocks and shifts'of the natural landscape- like your knees do for your body. A rigid wall cannot do this. A rigid wall without a footing is like a person without feet or knees that bend. It doesn't matter that the back pressure will be lessened, gravity still applies. The wall you propose will be top-heavy so even slight pressure could topple it.

Another point was brought up by laag - frost heaving. A concrete block wall will crack via differential settling unless you have a foundation wall going down to frost depth. And in zone 5, you are likely to have multiple freeze/thaw cycles over the course of the winter. (Frost depth varies, btw - in northern Illinois, it is generally considered to be 3'-6" below grade, while southern Wisconsin I believe uses 4'-0" as a minimum. Other locations in zone 5 are probably similar.)

This is the primary reason that segmental retaining walls (described by Mojave) have become so common. They move with the freeze thaw cycle, allow water to weep through, don't require deep excavation, and don't need a secondary treatment for aesthetics (if you are willing to accept the aesthetic of the block it self).

If you try to attach cultured stone to it, the attachment will fail with the movement of the wall.

The mechanism that is used by these walls is not exactly as someone mentioned above. These are what is called a "gravity wall". The mechanism has less to do with setting its feet or leaning into the slope and more to do with mass. The theory is to build enough mass into the wall to overcome the force against it. This is most often done using "geogrid". Many people believe that geogrid holds back the blocks from toppling over. Instead, it is tying the soil or gravel behind the wall to the wall to add to its mass. That material essentially switches teams (not that there is anything wrong with that) and works with the blocks to counteract the force applied against it instead of being part of that force that is acting against the wall.

The poured concrete or mortared block wall on a footing works in an entirely different way. Ever step on a rake? It is what is called a cantelevered wall. The strength is determined in part by the width of the footing. The wall must be tied into the footing as Mojave explained. The wall sits near the front of the footing with the greater part of the footing extending back toward the retained land. This forms an "L" with the wall being the vertical element and the footing being the horizontal. It works like a chair. YUou can easily push a chair over by exherting force to the top of it and pushing it backward. The backfill is placed on the footing much like placing your butt in the chair. The mass holding down the bottom of the "L" keeps the vertical part from toppling over. It is much harder to push a chair over when someone is sitting in it vs. when there is not. And chairs fall over very easily when you hang your jacket on them, don't they?

Now, have you ever stepped on a rake? Cantelevered walls work pretty well don't they?

I wish to extend a hearty thank you for all who took time to answer my post. Your responses were educational, presented in lay man's terms and well thought out. It is much appreciated.

That said, I have decided building a wall as mentioned above would not be in our best interest. I'm sure I could fabricate a block wall to last for "x" amount of time, but between new England winters and a high water table, I could not see good things happening after a couple years.

As for pre-formed retaining wall blocks, let's just say that for the money those would cost (just material) we could do a heck of a lot around here. So it looks like it's time to "dress up" the boulders with a nice selection of conifers, rose bushes or whatever else she can think of.

Again, thank you.