My guess is that this piece dates to the second half of the 19th century--based both upon looking at a lot of other wooden pull toys, and also the fact that the U.S Calvalry was established as an official branch of the United States Army in 1861, becoming a major presence in extending United States governance into the Western states, especially after the Civil War. (The U.S. Cavalry insignia of two crossed sabers, which appears between the letters U & S. on one side of the horse, was adopted in 1851.) I was thrilled to find this piece at an antique shop in Waltham, MA, where I think it had just been delivered. Really a special thing with a fantastic presence; I'd put it somewhere where I'd see it every single day.
9 1/4" long x 8 3/4" tall x 3 3/4" wide and in great condition, with a terrific patina. There is one small split in the surface of the wood of the back leg visible on one side, which I don't think detracts at all.