Comment by Balgair

Typically, no. There are some municipalities and areas of road where there is a minimum speed limit, but in the US, those are very rare. Granted, a law enforcement officer has wide jurisdiction to determine if you are 'safe' to drive and a low speed may become unsafe. But they are unlikely to ticket you and are more likely to try to help you out. Driving under the speed limit may be annoying, but it is nearly-universally not illegal.