Novel, first published: Del Rey/Ballantine 1978
A cat-faced alien lands on a retired college professor's property and litters it with time tunnels. A mastodon blunders through, and the college professor and his practical-minded girl friend get the idea to form Time Associates, a time travel company. They also proclaim the new nation of Mastodonia to beat the IRS and establish residence in the past. When the company organizes its first safari, their troubles begin. The fledgling company must fight off politicians (who want to relieve the population problem by sending unfortunates into the past), the State Department, and the churches who, of course, want to travel to the early Christian era. After State puts a ban on time travel, riots break out, and Mastodonia is recognized as an independent state. When the alien leaves, he grants the professor the power to engineer other time roads.
Ewald, Robert J.: When the Fires Burn High and the Wind is from the North, p.115