You were given these clues to identify National Park Mystery Spot 19:

This place in a park has a place to park.

Up and down the children go.
Parents go along or watch from below.

Climb to the top if you have a yen
To cast your gaze on a lake named Glen.

The sand is her; she's not flesh and fur.
Or so some people have said.

From this you should have been able to deduce that the mystery spot is the Dune Climb at Michigan's Sleeping Bear Dunes National Lakeshore.

Here is how the clues work.

The conveniently-located Dune Climb sits next to the main road (Highway M-109) just north of the popular Pierce Stocking Scenic Drive loop. While visitors can climb sand dunes in other places within the park, the Dune Climb is the only place where dune climbing is encouraged and made convenient by the provision of special facilities, including a large parking lot (this place in a park has a place to park), a large picnic area, restrooms, a snack bar, and even a visitor center. On a warm summer day, there may be hundreds of people climbing the dune or just watching.

Although the Dune Climb is a family friendly place, the climb itself is steep and strenuous. Youngsters like to charge up the hill, passing older folk who are struggling and resting. Then, many of the kids (and not a few frisky adults) run and leap and bound and whoop and holler their way to the bottom, letting gravity do most of the work. Many parents don't make the climb, preferring to just turn the kids loose at the bottom and watch them have their fun. "Up and down the children go. Parents go along or watch from below."

A gorgeous panoramic view awaits those who may make it to the top. The scenery includes not only giant dunes, Lake Michigan, and North and South Manitou Islands, but also picturesque Glen Lake. "Climb to the top if you have a yen to cast your gaze on a lake named Glen."

The Native American "Legend of the Sleeping Bear" has it that the two offshore islands now known as North Manitou Island and South Manitou Island mark the spot where two bear cubs drowned as they tried to swim with their mother from the Wisconsin side of the lake where a great forest fire had forced them to take to the water. The great dunes on shore mark the spot where the mother bear fell asleep as she waited in vain for her lost cubs to arrive."The sand is her; she's not flesh and fur. Or so some people have said."

The "Yooper Highrider" photo that accompanied the mystery spot puzzle was something of a red herring, but could be construed as relevant. In Michigan vernacular language, a "Yooper" is a person who lives in the state's Upper Peninsula, a region commonly referred to as "the U.P." Though the Michigan connection is relevant, the regional connotation is not. Sleeping Bear Dunes National Lakeshore is mot in the Upper Peninsula. It is in the northwestern part of the Lower Peninsula.

Postscript: The Dune Climb is open for sledding in the winter, and when conditions are right it reportedly offers one hell of a ride.