From the Super Mario Wiki
Mushridge, alternatively referred to as Mushroom Ridge, is a small, western town located either in or near Sudden Death Valley. Little is known about Mushridge, as it was mostly mentioned in passing, and was actually seen only for a very short time. Mushridge was only ever seen in The Super Mario Bros. Super Show! episode "The Provolone Ranger".
At some point, Billy the Koopa plundered the citizens of Mushridge out of all their Gold Coins. Upon hearing about this, Princess Toadstool set out to reimburse the town by bringing them a trunk full of Gold Coins on a stagecoach, accompanied by Mario, Luigi and Toad.
While passing through Sudden Death Valley, the stagecoach was ambushed by Billy the Koopa and a Koopa Troopa, who kicked Mario off and hijacked it. Mario eventually met up with Pronto, and became the Provlone Ranger in order to save his friends and the Gold Coins from Billy the Koopa.
Afterwards, Mario brought the Gold Coins to Mushridge, and left before the citizens of the town were able to thank him and invite him to dinner. Upon hearing the mention of dinner, Mario came rushing back to Mushridge, stating that he ran even faster than Pronto.