Most states don't allow cycling on interstates, but unpopulated states such as South Dakota, North Dakota, and Montana don't have many choices. There are only a few roads that go across the state and all are interstates

Eventually I got comfortable riding on the highway next to speeding traffic. However I got myself in trouble in Washington state. I was in a rush to get to Seattle fast, so I chose to stay on the highway even though it was illegal. Eventually I'm riding with 5+ lanes of traffic on my left....and then 4+ lanes merge on my right. I'm cycling in the middle of an interstate highway with cars passing me at 55+mph on both sides. I was terrified!!! Thankfully a cop showed up just in time to pull me over and save my life. Thank you officer!