Areas That Are Open To The Public:
There are many areas besides the ones designated as open areas that are available to the public for gold prospecting.
These areas are governed by the U.S. DEPARTMENT OF THE INTERIOR, BUREAU OF LAND MANAGEMENT, and have been classified as being available for mineral location (entry). If the mineral rights are not owned by another entity, you can prospect on the property within any rules governing the type of mining allowed, or you can obtain the mineral rights by filing and recording a mining claim.
Any citizen of the United States, a minor who has reached the age of discretion, a corporation, and non-citizens (aliens) who have declared to become a citizen may locate and file a mining claim. The claim can be located on federal lands (BLM and Forest Service) that are open to mineral location (entry). To determine if a specific location is open to mineral entry you can check with the BLM state office for that area.
If you serialize a mineral claim, an annual filing must be made on or before September 1st of each year to maintain the claim/site. If you have more than 10 claims you must pay a $125 maintenance fee. If you have 10, or fewer claim/sites you may file a small miners waiver in lieu of the maintenance fee payment. If you choose to do that you must also perform $100 worth of labor or improvements during the assessment year (September 1, noon through September 1 noon). An assessment work notice (proof of labor) form must be filed on or before December 30, along with the $10 filing fee per claim. Contact your local BLM office for activities that qualify for assessment work.
The internet is an excellent way locate the BLM offices in your state. Contact them for the locations of land available for mineral entry. If you are a new prospector, my recommendation is to begin by joining a club and using their claims. Filing and maintaining claims is much easier in a club environment where the responsibilities, and associated work can be shared. This I also learned through years of experience.
Also contact the mineral agency in your state for local information. You will find a list of state government agencies and the department name to contact for all the gold bearing states that have a mineral agency in “THE GREAT AMERICAN GOLD RUSHES”, Volume I in “THE GREAT AMERICAN SERIES” of e-books on gold.