I would pick the Green Vase Zelkova. It is not a very common tree(at least where I am) and it has a beautiful arching canopy. It's often used as a replacement for American Elm because it looks so similar but doesn't have all the problems the elm has. It also has great rusty red fall colour.

Acer saccharum 'Majesty'
Majesty Sugar Maple
ZONE 3, HT 60', SP 50', SUN An abundance of branches, perfect symmetry and vigorous growth habit make this a favorite among the sugar maples. Dark green leaves resist sun scorch and turn to a vibrant orange red in fall. Like all sugar maples, it is not fond of heavy clay and need well drained soils.

Reading thru the information on this one, it mentions that it is a prolific seeder. That translates into a lot of gutter cleaning IMHO.

Here is a link that might be useful: European Hornbeam

Common Name: Linden, Shamrock
Scientific Name: Tilia cordata 'Baileyi'
Zone: 4
Light Requirements: Sun
Height: 40-50'
Width: 30'
Shape: pyramidal, broad
Foliage Color: dark green
Flower: yellow
Fall Color: yellow
Fruit: nutlet
Description: A vigorous growing Littleleaf Linden with stouter branching and a more open habit.

First the negatives:
Maples are prolific seeders as well as having heavy leaf litter that tends to mat if not removed quickly. They also have a very dense root system near the surface, tending to dry out the area beneath them, leading to droughty soil under the canopy where it is difficult to sustain lawn or groundcover.

The Swamp Oak likes wet conditions -- no great surprise. A beautiful tree that would not be happy on the street.

The Locust tends to be a shedder of tiny little leaves that are very hard to remove from the lawn and is very overused at strip malls.

Ornamental pears are shortlived -- I'm not familiar with this cultivar, but the commonly used Bradford Pear has a bad (and consistent) tendency to split down the center after 10-15 years.

European Hornbeam tends to be a small, shrubby tree very useful for tightly pruned, closely planted hedges.

The Zelkova is beautiful and less common, but does have a short trunk, meaning that the crown spreads out from a fairly low level unless pruned early in development. However, IMHO such pruning mars the beauty of its natural habit. Zelkova is a great specimen for the lawn, but I wouldn't confine it on an easement.

Positive:
The Linden is fast growing, low littering, adaptable, and has fragrant (though small) spring flowers. We planted a 2" diameter, 10' tree, 7 years ago, that is now nearly 20' tall. The pyramidal crown makes it a great street tree as well.

Good luck!

I say the linden also, the flowers smell great and they ( the flowers) that is make a great tea saw many in Romania along the streets and boulevards

One think I would suggest is looking around your neighborhood and seeing what kinds of trees are already planted and choose something to add to the diversity.

I disagree with the previous post that the Swamp White Oak would not do well. It is become increasingly popular on street tree lists for it's tolerance of dry soils, compacted soils and salt. It does not like alkaline soil.

My block here in Minneapolis is a honeylocust block. Mixed feelings about it. It is overplanted and has pest problems, but the ones on my block are very nice. Also, you don't really have to clean up after them. The tiny leaflets just disappear into the grass.

Thanks so much for all your input - I think maybe we will really consider the linden, the zelkova, or the oak. It would probably be a better idea to select one of the first two, since I don't believe there are many in our neighborhood (according to my husband, there are a lot of ash, a few oaks and some maples - I've never been able to identify a winter tree). Maybe putting in something a little more unusual will prevent every tree in the neighborhood from being wiped out again by a new ailment in twenty-five years. And something that flowers would really be very nice.

Thank you all again!

Too bad about the Ash, I suspect they will go the way of the American Elm soon, I'm afraid. Don't Lindens sucker at the base a lot?

We've got many Lindens within walking distance of our house. They really do smell great and of the list you posted, it would be my choice.

Though were I in your situation I might consider looking through a book of trees to see if there might be something I would like better, even if I had to pay for it myself. Afterall, a tree is something you will have to live with for a long time.

I will say that the ash tree on the fenceline between me and a neighbor is doing fine, which is a shame, because I would replace it with a Ginkgo. (I'd move the Ginkgo from the front yard to where the ash currently is)

~Chills