I thought I read somewhere that MK runs the 4th of July Fireworks on the 3rd of July as well as on the 4th. Is it true???? Magic Kingdom will be open until 12:30am on the 3rd.....why so late? Do any parks run their 4th of July displays on the 3rd???? Thanks !! 

I don't know if it's true or not. I asked the OP where he heard that and he didn't reply. We switched our plans to MK on 7/3 and MGM on 7/4 because we wanted to see their fireworks since they don't run often. I'm interested to see if anyone knows the answer!
OH, and that was the most people in one place I've ever seen in my 24 years.
According to a very reliable internet site,the holiday fireworks are supposed to be shown both July 3 and July 4.The announced Magic Kingdom hours are the same for both July 3 and July 4{9:00 AM-12:30 AM with fireworks at 9:00 PM}so I think the information is correct.Have a GREAT trip! 
Thanks for the info! Any way you can tell me what that site is? Always looking for more WDW info!
DH calls me a Disney junkie!
He'll come home 2 weeks after we get home from WDW! Just had to say it! 