At the Black Mailbox (between mile marker 29 and 30 on Hwy. 375) take the dirt road ("Mailbox Road") south. After 3.9 miles you pass a cattle water hole to your right and come to a 5-way intersection. Take the second road to the right (going almost straight) for another 1.1 miles. At the stop sign at the intersection with Groom Lake Road turn right and follow Groom Lake Road for 8.6 miles to the border.
For more information see our Tikaboo Valley Map.