This image shows an unusual subject, a simple but radical curve in a highway in Oklahoma. Because of the greater than 180 degree turn in the road, these features are pretty much universally described as horseshoe curves.

Color by Bob Taylor
The description states:
HORSESHOE CURVE
This beautiful curve is located on highway 77 in the Arbuckle Mountains near the beautiful Turner Falls recreational area. Also close by is Price Falls.
–The description places this road feature in south central Oklahoma. Turner Falls are not particularly imposing at only 77 feet, but are tied for the highest waterfall in Oklahoma.
This postcard likely dates from the 1960s.