Swedish aspens will grow fast and in a narrow, columnar shape. Mine are about 30' tall after six years of growth. Only about 5' wide. They can send out some suckers (sprouts off of the roots) but not as many as traditional quaking aspens.

There are plenty of other columnar trees, including maples and oaks, but they probably don't grow as fast as these aspens. The downside is that most fast-growing trees are shorter-lived than the slower trees. I think the Swedish aspens should live 20 years or so, which is plenty long for a typical homeowner's tenure in a home. But if you want to plant permanently for future generations, pick a maple or oak.

These are all deciduous, so they don't provide much privacy in winter. You can also find some columnar evergreens, including firs, spruces, and pines, but I don't know them as well. A good local nursery should be able to help you pick the right tree, if you tell them the characteristics you want (how tall, how narrow, how fast it should grow, evergreen vs. deciduous, etc.).

paula_rose, how tall do they need to mature to in order to work for your situation? Are you hoping for evergreen or will a dense deciduous work? If a deciduous, relatively fast grower to 6'- 9'h. x 2'w. will work, I'd suggest you may want to look into Rhamnus frangula 'Fine Line'. This is the plant I will probably get for the same purpose. You could actually stager two rows in the narrow 5' area you have, to obtain even more privacy.

Crystal

I have known persons to plant at least two rows; a tall evergreen and a row of something like a Lombardi poplar. The poplar provides some coverage until the evergreen has time to establish itself then it is removed.

I have also know persons in Utah who get quite upset when the neighbor erects an obstruction to their view.

Thanks for the suggestions everyone.
We're in talks with my in-laws landscaper to see if we can find something we really like...although i just read a previous thread on bamboo, we will look into that too.
We only need the growth to be about 8 ft. tall
Not to worry Albert135, we are not obstructing their view, as our yard runs east/west, the views are all of the mountains- east!