Travel distance from Las Vegas to St. Thomas Point is approx. 80 miles which take 1.5 hrs to drive.
From Las Vegas drive north on I-15 and turn east onto SR169. You'll drive through the Valley of Fire State Park and after crossing SR167 the road becomes NPS-109, a dirt road that leads to St. Thomas Point.
Certainly you can drive the SR 167 from Vegas directly in order to reach NPS-109.
A Ranger is sometimes at the parking lot and has further information; otherwise: the short hiking loop to St. Thomas takes 1 to 1.5 hrs and is categorized easy to moderate.
Expect to get muddy after it had rained in the area. Check on the NPS website (see Link below) or call a ranger station to learn about accessibility of the road to St. Thomas Point.
Following NPS-Link "Lake Mead National Recreation Area" provides also a map for the area, please check the topic: "Plan Your Visit".
1
-- St. Thomas Point, Nevada
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Lat: 36.46916 / Lon: -114.38475
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2
-- NPS-109 begins here
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Lat: 36.440774 / Lon: -114.4275
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3
-- Las Vegas
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Lat: 36.114858 / Lon: -115.173111
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