The answer is:  some counties in some states have on-line resources.  Some don't.

Sometimes you have to pay for access, sometimes you don't.  Sometimes you have to sign up with the Register of Deeds and then pay per copy.  sometimes you have to open an escrow account and put money on file.  Sometims you can look at the index, but not the documents unless you pay.  Etc. etc.

 Sometimes the records go back (on line) just a couple of years; sometimes they go back 40 plus.

Sometimes it is safe to search on line, sometimes it isn't.  (The counties I search on line actually share the same server as the Reg. of Deeds office so it makes absolutely no difference if you're sitting at THEIR computer terminal or yours.  One county here in Michigan is run by an outside source and is totally unreliable according to the abstractors who've run title there.)