The term California Gold Rush entered into our history reports in the late 1800's as best as I can tell. I was going to take the time and outline key events of the Gold Rush but came across a web page that has already done for us. The search for Gold helped in the expansion of California and in points west. It dated from 1848-1859.
California Gold Rush Timeline
And don't ignore sites written with children in mind. Sometimes it helps to simplify points by reading over such websites. Kidport Reference Library They also have a lot of links to other sites.
And if your looking for a story and how the California Gold Rush affected some of the towns, Munsey Magazine, Vol 10 has an article Mr. Justice Field located in Google books.