Where can you find the tallest sand dunes in north america?

In Colorado, Alamosa, North America.

Explanation:

The Great Sand Dunes, in southern Colorado, are the tallest in North America, with a few dunes towering over 700 feet. it features 30 square miles of rolling sand dunes along with incredible high-elevation mountains.

The dune takes two hours to climb.On March 17, 1932, the Great Sand Dunes were designated as a National Monument. It was until the 2000, that was when the Great Sand Dunes were considered a national park and preserve.

Colorado

Explanation:

Colorado has the tallest sand dunes in North America. The dunes are really high and can reach about seven hundred and fifty feet tall.

The sand dunes of Colorado were originally formed when the large lakes that once covered the region dried up, leaving behind all the sand. The dunes are eroded reformed daily by actions of wind and water erosion.