From Las Vegas take I-15 north for 22 miles. At exit 64, take US-93 north. After 85 miles, 12 miles past Alamo, you come to the intersection with Hwy. 318 on the left. Directly across the road from the intersection, to your right, you will see the remains of an old casino.
At the intersection, turn left onto Hwy. 318, and after less than a mile veer left again onto Hwy. 375. At that intersection you will see the "Extraterrestrial Highway" sign under a group of trees. Right next to the sign, in the shade of the trees, is where some of the Area 51 workers park their cars to take the white bus into Area 51.
From the beginning of Hwy. 375 it is about 15 miles over Hancock Summit to the beginning of Groom Lake Road, 20 miles to the Black Mailbox and 40 miles to Rachel.
The last gas near Las Vegas is the Love's gas station at the intersection of I-15 and US-93. There are a couple of gas stations on the way, in Alamo and in Ash Springs. There is no gas in Rachel, or anywhere along the 150-mile stretch between Ash Springs and Tonopah. So you may want to keep an eye on your gas.
Please note that most of Hwy. 375 is open range. There are no fences, and cows frequently wander across the road. When you see cows near the road slow down and be prepared to stop. Be especially careful at night, when cows on the road are very hard to see. Running into a cow will not only cause severe damage to your vehicle, but you will also have to reimburse the rancher for the cow. And it is usually his most expensive cow...
For a more detailed map of the Rachel / Groom Lake area click here.