A rat pit was a small enclosed arena built to hold a terrier and rats. In the days before PC culture, and particularly in Victorian England, it was a common blue collar sport. Built in a gambling den, bets were placed on either the number of rats that dog could kill or the time it needed to kill them.
In Britain in 1835 a cruelty act was passed that made other forms of live animal fighting such as bulls, and bears illegal, but not rat pits. As a result, ratting pits became the premier form of blue collar gambling entertainment.
The rat pits also engaged traditional rat catchers as the rats used were not tame bred captive rats but wild live caught rats. This allowed the rat catcher to make an extra buck selling his daily catch to a ratting pit.
The last public rat pit was in 1912 London and the owner of the event and location was prosecuted. There are many famous pit owners, rat pits, and pit dogs
Billy and Jacko are both very famous rat pit dogs. Kit Burns, who ran his own dog fighting arena in New York City also owned several famous dogs.
“Of all the baiting sports which have now been made illegal, I only regret the passing of rat-pits. For one thing, I hate rats and anyhow their end was extremely sudden. For another I love to see a good dog kill rats and I have caught them for a hobby since I was a lad.” Phil Drabble, Terrierman
Full article on rat pits by Phil Drabble