They're scavengers. So if you want to get rid of them, get rid of your compost pile.

Millipedes, like many other similar insects, live where there is a good environment, cool and moist, and ample food sources, decaying vegetative waste. Millipedes are harmless to humans and are resistant to most all of the pesticides there are which will do more harm to you then them.
The simplest, and most environmentally friendly, means of control is your foot followed a long way down the list by your vacuum.

Here is a link that might be useful: Millipedes

It's hard to believe that Iowa State University's Dept of Entomology would include millipedes in their "Iowa Insect Information Notes"!! They're not insects.

Millipedes are Diplopoda, but most people see all bugs(small thing crawling around) as insect. So they are included. IMO.

I'm going nuclear... This morning I spread bugbgone and watered it in with one of the bugbgone liquids that you attach to your hose. I also used some Diatomaceous earth.

If this was just a few bugs I wouldn't do this but I'm infested. Tonight there were just a few. Hopefully I've stopped the infestation.

So far so good. Just a few on the patio last night and none made it into the house.

The primary, active, ingrediant in Bug B Gone is a synthetic pyrethroid and probably is no more effective then a less expensive pest control product made from natural pyrethrins.

Someone posted last year about a millipede invasion, and I remember some truly gross pictures and descriptions, so this rang a bell.
For some reason, they are known to do this. Google "millipede migration" and see what's there. Yuck.

"The primary, active, ingrediant in Bug B Gone is a synthetic pyrethroid and probably is no more effective then a less expensive pest control product made from natural pyrethrins."
Seems to have worked and they had it Lowes.

I'm claiming victory on this one!!!

Just fix the door seals and let them be. They promote aerobic metabolism, good bacteria and fungus. Consider it a good thing for now because they will distribute organic matter all over your yard, which is something you couldn't pay a company to do like Gods little creatures can. They have had a coincidental season which has allowed them to populate vigorously so I would let them do their thing because they will be gone next season and your soil will be much more rich in nutrients because of them. If it were me, i would put away the chemicals.

Arthropods, related to shrimp, lobster, crayfish. Shredders - they shred vegetation. Seems like they are beneficial. They migrate en mass for two weeks. The problem is the door seal, not the millipedes.

"let them be"
normal amounts are fine. This was an infestation. The population is back to a normal amount (ie, I see a few)