The Mums in the Historical Society beds came back with such energy that they took over the beds and they had to go.
Mulch them well over the winter or cover them with a styrofoam cone. Just be sure to remove mulch from the center first thing in the spring so it can get air circulation. You can leave the mulch on the outer portion of the root system but the crown needs to be a little elevated.
Where I live it's sometimes 10 degrees colder than in town and they will not overwinter here, so if you have a warm protected spot, that's where they will stand the best chance of coming back.
You can also keep them in big pots in the ground, lift them in the fall and bring them into a sheltered garage or shed that has a little bit of heat and then put them back out in the spring. They will get bigger every year to the point that you can divide them.