To celebrate Tucson’s birthday, start off at the Luis G. Gutierrez Bridge (formerly the Cushing Street bridge) west of the I-10 at 9:30 a.m. to watch a solar alignment of the overhead canopy cut- out design (see photo below) onto the bridge’s floor. The Discovery Date marks the Birthday of the Tucson Presidio, San Augustin del Tucson.

This is what is written on the bridge for this Discovery Date:
“The Walled Presidio San Agustin de Tucson, was founded by Hugo O’Connor (sic) on August 20, 1775 as a Spanish outpost. This date is historically celebrated as Tucson’s Birthday. Named after the O’odham village of “Chuck-son”, meaning “Village of the dark spring at the foot of the mountains.” Image from a 1850 woodcut by James Bell. (Dicovery Date and time: August 20, 9:30 a.m.)”
More info on their FB page: https://www.facebook.com/luisggutierrezbridge
Then later at 5:30 p.m. check out the Tucson Presidio itself at the SW corner of Church and Washington in downtown for their annual celebration.