Tall grasses.

Hmm... that is on the prairie. Conifers, ferns, and cedar were probably covering most of Missoula.

I don't know, but likely it was some form of taiga.

Where I live the dominant plant cover 10,000 years ago were pine trees.

A guess....redwoods.

In between the ice and floods our area was temperate rainforest. It's thought that the native americans controlled much of oregon with fire, turning much of our valley into a large oak savannah and prairie filled lots of food and game.

The dominant plant cover here was called "ice"

http://www.museum.state.il.us/exhibits/larson/glaciers.html

Buffalo grass.

That's what it says in the park next door.

Grasses and old growth forest, without a doubt. In Bayonne, saltwater marshland was much of it with some old forest on the ridgeline.