We live in Western Pa! Those are wonderful ideas. Thank you!

Yes, just turn into a hedgerow on your side. Fill in with natives and a few well-behaved exotics. Be sure to include a few evergreens (either BLE's or smaller conifers) and things that would appeal to wildlife: viburnums, hollies, hawthorn.

Is this a big yard such that there is a lot of space to plant things, whereas it would not be a problem to make YOUR hedge row substantially deeper? (It always helps to post a photo that includes the house, as this is the primary reference element in most residential landscaping.)

With neighbors who are uninterested in prettying up an area that is nearly shared, you are faced with creating your own development which covers up your view of their area. Keep in mind that you can do whatever you want to plants on your side of the line and and also to any part of any plant that crosses over the line onto your side. I.e., If a plant from their side sends a branch through the air and said branch crosses over the line (a plane that extends from the line, straight up into the heavens, you can cut the plant back to the line. Imagine a monster chain saw positioned vertically slicing right down the line, and that's what you could do but, of course, you would have to be realistic and do it by some "low gear" method .... loppers, hand saws, small chain saw, etc.

As mentioned, placing a privacy fence along your side of the line would give instant visual relief and make a good barrier to help with future maintenance. It would stop all of the neighbor's scruffy plants from reaching into your yard, up to 6' height. You'd still need to manually trim off what hangs over the line above that, or it would shade, and therefore stifle, your plants.

With or without a privacy fence, as Gardengal mentioned, you can make your own hedgerow and it can be whatever you want it to be. It can be like a foundation planting, using the fence as a visual backdrop. if you want. Or it can completely screen the fence in time, if that's your preference.

you can do whatever you want to plants on your side of the line and and also to any part of any plant that crosses over the line

Check local laws to confirm before assuming this is automatically the case.

Thank you all for the wonderful ideas! We do have a lot of space to work with on our side, so we will keep an open mind about all suggestions! Please ignore the muddy yard, we are filling it this summer (it used to be a pool)

"Check local laws to confirm before assuming this is automatically the case."

That one's property, and property rights, extend in a vertical plane from the lot line (both into the ground and up into the air) is basic real estate law and applies to all property boundaries (at least in the US.) There is no local law that can countermand this. If it were not this way, a giant, unending can of worms would be opened and endless arguments between neighbors would never be resolved. The lot line says, "this is the end of what you own!" It is a fantastic invention that preserves the peace.

A nice hedgerow of 12' height, min., shrubs is all you need.

Editing to add an illustration (from https://financial-dictionary.thefreedictionary.com/landlessness) that sums up the concept of land ownership

To blend in with what's there - red-twigged dogwood shrubs have a stick appearance... in yellow also.