This image shows a parade ground at Fort Bliss, Texas with serveral large formations of cavalry as they approach the camera.

There is no description on the back of this card.
As this is a very large cavalry unit, and the standing army in the United States was not large before the First World War, it is likely that this image dates from the late 1910s, when units were being assembled for deployment overseas.
If this is the case, then this is most likely the 15th Cavalry Division, large portions of which were stationed in Fort Bliss in 1917 until deactivation in 1918.