Don't forget about river birch and willow. Willow is generally not as long lived and not as "windfirm," but both trees will tolerate wetter soils. Baldcypress is great until it sheds in the fall and your retriever walks through it, needles sticking to its fur and covering the floor! Nonetheless, a great tree.
hortster

If it is hardy for you, Illicium floridanum tolerates wet soil.

I'd omit the Japanese maple - these are very picky about good drainage. If you want to include a maple, try Acer rubrum, as it is very tolerant of wet soils (one common name is "swamp maple"). Sourwood, Nyssa sylvatica, is another good choice.

What do you guys think about southern magnolia in such a situation? They generally do well in our climate.

Southern Magnolia needs special situations to live here so I had to go look this up.

"Culture

* full sun to shade
* soil tolerant
* transplant from container or B&B, difficult to transplant
* prune after flowering
* prefers rich, well-drained soil
* somewhat drought tolerant"

My guess is it will linger but not thrive. Perhaps there is a cultivar which grows well near the edges of southern swamps.

Weeping willows grow VERY FAST and maintain a thick structure here over winter so they screen pretty well. If one must hide something n a damp area FAST they are a good choice. Trouble is they don't last human generations.

A double tiered screen could give you some mature other trees by the time the willows are goners.

BTW, the metasequoias are the neatest thing since Photosynthesis IMO

Here is a link that might be useful: Hort.uconn Magnolia grandiflora fact sheet

It would be nice to know about where you are (other than zone 7).

Magnolia grandiflora is not specifically known for tolerating wet soils that I know of. Magnolia virginiana, however, is well suited for that.

Other potentially evergreen choices: Atlantic whitecedar (Chamaecyparis thyoides) and Dahoon holly (Ilex casine).

I love Atlantic white cedar, but it hasn't been particularly fast growing for me. Magnolia grandiflora doesn't grow in swampy areas here, but they DO thrive in areas that are occasionally real wet. They're about as "windfirm" as you can get, ranking right up there with live oak - I didn't lose a single one after Hurricane Katrina, and they're growing all over my property, very fast, I might add.
Do you like sweetgum? Some people hate the seed balls, but I don't mind them, and they can certainly tolerate wet soil, plus thrive equally as well during dry periods. They grow very fast, and they're the main host plant for the beautiful luna moth - luna moths lay their eggs singly, here and there, though, so they'll never decimate your trees.
Willows are good, but I've found that they need constant moisture, so if your site ever dries up, you may lose your trees.
Red maples grow fast and love wet conditions, as do sweet bay magnolias. Of course, bald cypress and dawn cypress are good for those conditions.
Sherry

I am in the state of Virginia. I want to say that the area is not a swamp. It is not as fast draining as the rest of my garden but currently several hollies, native deciduous azaleas, a red oak, and some old fashioned roses are happily growing. I need probably one large evergreen tree and perhaps another deciduous tree. The idea of a willow actually sounds appealing. Around here, they provide almost year round screening.

Would second the above mentioned Sweet Bay Magnolia for a wet area, Southern Magnolia might be iffy there.
If you already have hollies growing successfully, why not choose the Holly you've mentioned.