So I can forgive Prof. Collins that oversight, but not the split of California in 1859. Southern "Californios" were so concerned about the massive influx of gold rush miners in the north, they pitched the idea of splitting California. And in 1859 the California legislature DID consent to split the state in two. The U.S. Congress did not act, but the state did, an important landmark that is often forgotten.
And if we want to get technical, there have been dozens of times that states have consented to give up small bits of territory. For example, in 1977 Texas gave away land to Mexico near the city of Rio Rico. So hopefully the Denver Post will issue a correction, and Prof Collins will pick up a copy of Lost States ;)
by Michael Trinklein