Florida.

I went on maternity leave fully believing that I had a job to come back to after my standard 6 week leave. I went back and my employer laid me off.

Can they do this????

Your are entitled to 12 weeks of unpaid leave if you satisfy the following criteria.
The company you work with should have more than 50 employees within 75 miles of the site you work at.
You should have worked with the employer for a period of 12 months (which need not be consecutive) and atleast 1250 hours in the previous 12 months.

If you satisfy the above criteria then your company is in violation of Family and Medical Leave Act (FMLA).