And a large percentage of the people fined were Jews.
This happened throughout the decade; here's an article from 1925.
Like some speed traps today, it looks like this was used as a revenue generator.
Jews at the time would close their shops on Saturday, and Sunday was the most lucrative day available for them, and their customers were mostly Jewish as well, so it seems that many of them took the chance and paid the fine if caught.
One Jew in 1922 tried to fight back by claiming that he indeed closed his shop on the Sabbath, but the judge ruled that the Sabbath of the Bible wasn't the Sabbath of America:
One Jewish newspaper responded to this story with a joke considered old at the time:
The Sabbath laws, later known as Blue Laws, remain in force even today in many states although most have been repealed. The US Supreme Court has ruled that they are not religious and merely enforce a day of rest for the social good. The fact that Jews (and Seventh Day Adventists) are economically hurt by this was not enough to say that storeowners should be allowed to decide which day of the week to close.
