There are two main access points for Lake Powell: Page, Arizona to the west and the Utah marinas to the east.
From the Utah marinas: Follow Route 276 to Route 95 and turn left (north). Travel as far as Hanksville, Utah and then turn left (west) on Route 24. Follow for 38 miles to Route 12. Along this short stretch you'll zip through Capitol Reef National Park.
Turn left (south) on Route 12 and prepare the eyes for some high-five scenery. This two-lane road twists through the Dixie National Forest and the Grand Staircase-Escalante National Monument. Camping and hiking options abound. Just after the Escalante National Monument lies Bryce National Park.
At the Junction of Routes 12 and 89 turn south and drive for 44 miles to Mount Carmel Junction. Here, turn right on Route 9 and follow into Zion.
From Page, Arizona (116 miles): Take Route 89 west. After just 11 miles it will bend into Utah and then spill into the southern half of the Grand Staircase-Escalante National Monument. Continue on Route 89 until reaching Mount Carmel Junction. Turn left on Route 9 and follow for 12 miles to Zion National Park's eastern entrance.