Yes, Cindy, I need to divide mine too. I noticed last year that I had fewer blooms. So, I got out there and dug around the center that was clogged with roots and leaves. It had actually started rotting in the center. I cleaned everything out and added some clean sand in the middle. They look loads better this year and have just started blooming. I did move a few that broke off last year and those few are blooming, too. Mine are that big but I can see how it could be hard to get a big old clump out and divide it. I bet it likes your good nothern soil. I can't imagine a place where they wouldn't be pretty. I just love their color. It's awesome.
Before you start to divide your next clump, if it's not damp, water it good the night before. This can really make a difference in moving any deep grown roots. If it's really dry, I'd water it every night for a week and then dig it up. You don't want it muddy but damp soil sure does move easier.
