You just need a piece of land and a lot of saplings. Most trees can take care of themselves once planted.
The total area of forest land in US is 501 million acres, with 2.5 trillion trees of all types.
So you'd need to just find 207 million acres of viable land, 1 trillion saplings and enough people to plant them.
In my point of view, that's a bit challenging - but I'm no expert in such matters.