Is it legal for a landlord to charge me double the amount of the usual deposit because I had little rental history?

The Fair Housing Act doesn't apply to your situation. However there may be state law that applies. Some states have laws that limit the amount a landlord may ask for as a security deposit. For example, in NJ the landlord cannot require a deposit of more than 1.5 months rent.

There is a sticky at the top of the Real Estate Law forum with links to the laws for all 50 states. Take a look to see if your state has any law that applies.

Yes, the landlord can charge you a higher security deposit because of a bad or insufficient rental/credit history, provided that the amout charged is not in excess of the amount permitted under your state law. Here in AZ the deposit cannot be more than 1 1/2 times the monthly rent.