(KFYI News) – Maricopa County's Tent City Jail turns 21 on Sunday.

The tents greatly increase the capacity of the jail system without the expense of building brick-and-mortar structures.

Sheriff Joe Arpaio tells KFYI News that when he ran for sheriff for the first time in 1992, "I promised in my campaign... I will put up tents.  So on August 3, 1993, I put up Korean war tents, and they're still there after 21 years."

Tent City has weathered frequent criticism and even lawsuits from organizations like the ACLU and Amnesty International, which argued that housing convicted inmates in outdoor tents, especially in the 100+ degree temperatures of the Arizona summer and temperatures that sometimes dip into the 30s in winter, amounted to cruel and unusual punishment.  Arpaio's office has won all of the challenges and lawsuits.

The sheriff likes to argue that with thousands of US troops living in tents under similar weather conditions in other countries – "and they haven't even committed a crime" – it's certainly not cruel to have inmates living under the same circumstances.

Over the past 21 years, a lot of inmates have called Tent City home.  "We've had over a half million serve time, including some celebrities," Arpaio says.

Other celebrities have visited the tents, according to Arpaio.  "I've had four presidential candidates visit me in the tents when they were running for President.  Of course, they all lost," he chuckled.

To celebrate the milestone, Arpaio invited about 15 inmates who have all turned 21 this year to share some birthday cake and Gatorade with him, noting that they were all barely born when Tent City opened its fortified gates for the first time.