This blog explores the history of Phoenix, Arizona and a little bit of Los Angeles and San Francisco, California

From ancient riverbed to downtown Phoenix - Block 23 underground parking



Time travel with me to downtown Phoenix before anyone, including the Hohokams, arrived in the Salt River Valley. Let's go to where Block 23 is nowadays.

If you're a fan of Phoenix history, you know that downtown was platted in 1870, and went from Van Buren to Harrison and from 7th Avenue to 7th Street. Each block was numbered, except Block 23, which simply said "Plaza". It's where the City Hall Plaza was, and then in 1931, where the Fox Theater was built, and in 1953 where JC Penney's was built. Specifically Block 23 was between Washington and Jefferson and 1st Street and 2nd Street.

Phoenix, Arizona Territory Block map 1881.

I've driven past Block 23 for years and never gave it a second look. To me, it was just another parking lot in downtown Phoenix. And then I discovered the underground parking garage. And then I found out that it had been built in 1953. And today I discovered that the construction was very difficult for the Del Webb company because of their battle with sand. They were digging into an ancient riverbed.

The underground parking garage under construction in 1953. You're looking northwest from 2nd Street and Jefferson. Block 23.

The riverbed, of course, was the Salt River. And if you look at a map, you can see that the flooding must have been enormous in prehistoric times. It's the reason why there were so many mesquite trees that had to be removed before the townsite could be platted in 1870. It was a riparian area.

Dense Growth of Mesquite, 1870

Of course, this type of flooding continued on, and the engineers got to work to control it. In 1883 Grand Canal was dug, then in 1885 the Arizona Canal. In 1911 a gigantic dam was built on the Salt River, called Roosevelt Dam. By the 1950s, the Maricopa County Flood Control District was getting most of the flooding under control, and by the 1990s the flood control was so complete that it actually surprises people nowadays to learn that Phoenix had been in a floodplain for so long.

But the sand is still there, as is the riverbed. And the next time you park in the underground parking garage at Block 23, take a moment and think about where you are, in an ancient riverbed.

Thank you for time traveling with me.


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