Why is Baseline Road called Baseline Road?

Baseline Road was a crucial part of surveying in Arizona. (Source: 3TV/CBS 5)

OK, a lot of this is geography stuff but I love maps and I’m going to charge ahead hoping there’ll be some general interest, too.

Baseline Road actually runs along the primary “baseline” for Arizona established by the Public Land Survey System. The original east/west layout was made in 1851 and starts at a place called Monument Hill. More on that later.

The road, Baseline, stretches continually for 43 miles across Maricopa and Pinal counties, which is pretty impressive for basically a straight line.

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of Baseline Road


The extension of the road’s farthest point west in Maricopa County is around 547th Avenue. But even where there’s no road, there’s a baseline.

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So what’s the big deal?

The east/west baseline coupled with the north/south baseline (more on that later, too) is what all land surveys in the state are derived from. It was a system developed in the 1700s and is the primary survey tool for most of the country. The earliest states, and Texas, were not included. Here is a U.S. map of different states and their baselines, including Arizona’s.

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U.S. with baselines]

Now what’s this Gila and Salt River Meridian we see on the map? That’s the north/south “baseline,” if you will.

And guess what road it runs along in the west Valley? Avondale Boulevard. And here’s what it really gets fun, the geography that is.

When the extension of Arizona's baseline meets the Gila/Salt Meridian, it is at a place you may recognize, especially if you’re a race fan. You know that hill just east of Phoenix International Raceway (now ISM) where people pitch awnings and watch the races?

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It’s called Monument Hill. And if you venture to the top you’ll see this:

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of Monument Hill ]

And take a look to the north. There's Avondale Boulevard with the Gila River in the foreground.

[MOBILE/APP USERS: Click/tap here to see photo of Avondale Boulevard]It's the single spot in the state where all land surveys emanate.

Bet some of you race fans never knew you were sitting on an important part Arizona land history.

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Copyright 2018 KPHO/KTVK (KPHO Broadcasting Corporation). All rights reserved.

Arizona’s Family Chief Meteorologist | Arizona’s Weather Authority

With 25 years of experience forecasting weather and his vast knowledge of Arizona and its micro climates, Royal is an Arizona Weather Authority.

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