My landlord refuses to release my rental history until I gave a 30 day notice to vacate. When I gave such notice they still didn't release my information. The house I was trying to move into was sold to another buyer since my information couldn't be obtained. Is this legal?

They don't HAVE to release your rental history... its their option. Its like a reference... they can decline to say anything at all.if they want.

They don't HAVE to release your rental history....its their option. Its like a reference....they can decline to say anything at all.if they want.
That's crazy. It shouldn't be a requirement on an application for a new place if its optional on the other end.

Its optional on both ends... as far as the property owners are concerned. It's for their assurance you are a responsible person... they can require it if they want... and most of the smarter ones will run a credit history before renting or entering into a contract with you.

I'm guessing you don't have much of a credit history if not getting a Rental reference in time was enough for a deal to fall through.

I'd do some research on building a credit history... and how to build good credit. Its essential for so many reasons... even for ones you might not think are related. Such as employment and Insurance.

'Requirement' by one landlord (or even most) isn't to be confused with state law. And there are no states that I know of that have laws covering references or history.
It would have behooved you to present copies of canceled checks showing that you paid on time each month for X months. That's mainly what landlords are interested in. You could show pictures of how clean you are, I suppose, although that wouldn't mean anything to someone who realizes that you could be taking pictures of anywhere. You could have a copy of your lease and a picture of you standing in front of the house number and then opening the door of such number and so on.
Does your landlord have a reason for making your life difficult?