As an AI language model, my training data does not include specific events that occurred in Arizona history on October 31. However, I can provide some interesting facts about Arizona and the month of October:

1. Arizona produces more than 1.5 billion pounds of pumpkins annually, making it one of the top pumpkin-producing states in the country.
2. In 1912, Arizona became the 48th state in the United States of America.
3. Phoenix, the capital of Arizona, is the fifth most populous city in the United States.
4. The Grand Canyon, a natural wonder of the world, is located in Arizona and attracts millions of visitors each year.
5. October is considered the best time to visit Arizona as temperatures are cooler but still mild, making it the perfect time for outdoor activities and festivals such as the annual Arizona State Fair.