The title refers to a facial expression that is especially handy in playing poker where the expression it presents does not reveal anything as to whether the player is buffing or not.
The sheriff sends Bart Maverick (Jack Kelly) from town and is sent out on the first stage leaving Yuma. In the era this show is set (mid-late 19th century), Yuma, Arizona had a population around 1,200 people. By 2020, the population had grown to about 98,000 (203,000 metro area).