Jack of the United States has gone through 33 changes since 1776 the first Navy Jack (now only used as a navel jack by the oldest active warship) was used multiple times.
The jack of the United States is a maritime flag representing U.S. The design of the U.S. jack has consisted of essentially the canton of the U.S. national flag since the late 1770s, with each subsequent modification to the U.S. national flag's canton being represented in the U.S. jack as well. 
