Land- Land was relatively cheap, and there was a lot to go around. People were hoping to escape slavery, and start a new life with a business of their own, and owning land was a big help.
Gold- Gold People wanted to start a better lives for themselves, and finding a fortune was one of the ways to do so.
(added bonus: Resources! There were many resources available and ready for use, making heading west a definite on a lot of people's to-do lists)
