This is one of a pair of cow shoes worn by moonshiners during Prohibition to hide their tracks from prohibition agents. From a 1922 edition of The Evening Independent:

A new method of evading prohibition agents was revealed here today by A.L. Allen, state prohibition enforcement director, who displayed what he called a "cow shoe" as the latest thing front the haunts of moonshiners.

The cow shoe is a strip of metal to which is tacked a wooden block carved to resemble the hoof of a cow, which may be strapped to the human foot. A man shod with a pair of them would leave a trail resembling that of a cow.

The shoe found was picked up near Port Tampa where a still was located some time ago. It will be sent to the prohibition department at Washington. Officers believe the inventor got his idea from a Sherlock Holmes story in which the villain shod his horse with shoes the imprint of which resembled those of a cow's hoof.

I think I saw a woman wearing a pair of these on 6th Ave last week. (via nyer photo booth)