1. On May 10, 1869, the completion of the first transcontinental railroad was celebrated in Promontory, Utah, a significant event in Arizona history, as it allowed for easier transportation of goods, people, and ideas into the Arizona Territory.

2. On May 10, 1870, the Arizona territory's first newspaper, the Arizona Miner, began publication in Prescott. The paper provided residents with vital news and information about the developing territory, including the growth of mining towns, railroad expansion, and territorial politics.

3. On May 10, 1944, the Small Business Administration (SBA) was established in Arizona to provide financial assistance and expert advice to small businesses. The SBA supported the development of small businesses, which played a vital role in the state's economic growth.

4. On May 10, 1963, the city of Phoenix became the first city in the United States to adopt the modern six-digit phone number system. This change was necessary due to the city's rapid growth and the need to accommodate more phone lines and subscribers.

5. On May 10, 2019, Governor Doug Ducey signed a bill into law officially recognizing the Navajo Code Talkers, who played a critical role in WWII by using their native language to transmit coded messages that were almost impossible for enemy forces to decipher. The bill established August 14th as Navajo Code Talkers Day in Arizona.