Four Corners States: Where Arizona, Colorado, New Mexico and Utah Meet

The Four Corners states are Arizona, Colorado, New Mexico and Utah. Their borders meet at a single point on the Colorado Plateau, marked by the Four Corners Monument, and it is the only place in the United States where four states touch.

Two straight survey lines make the corner. The 37th parallel separates Utah and Colorado (to the north) from Arizona and New Mexico (to the south), and a north-south line separates Utah and Arizona (to the west) from Colorado and New Mexico (to the east). Each state gets one quarter:

The monument also sits on tribal land. Three quadrants are part of the Navajo Nation, and the Colorado quadrant belongs to the Ute Mountain Ute Tribe's reservation. Navajo Nation Parks & Recreation runs the site as the Four Corners Monument Navajo Tribal Park.

Look closely at the map and you can see that the state line runs a little west of the dashed 109° W meridian. That small gap is the whole story behind the most repeated myth about the place, covered further down.

The monument is at roughly 36°59′56″ N, 109°02′43″ W, about 5 miles (7 km) in a straight line from Teec Nos Pos, Arizona, the nearest community listed in the Census Bureau's place file. The National Geodetic Survey lists the survey mark there under the designation "CO UT AZ NM".

It is remote. These are straight-line distances from the monument to nearby towns and regional cities, measured on the WGS84 ellipsoid to each place's Census internal point. Road distances are longer, often by a third or more.

Several of the nearest communities, including Teec Nos Pos, Shiprock, Kayenta and Towaoc, are not incorporated towns at all. The Census Bureau tracks them as census designated places, which is explained in What Is a Census Designated Place?.

The corner exists because Congress drew territories with straight lines on paper, and surveyors then had to find those lines on the ground with 1860s and 1870s instruments.

1. The 37th parallel. The line between Colorado Territory and New Mexico Territory follows the 37th parallel north. The General Land Office had Ehud N. Darling survey it in 1868, and the Supreme Court later confirmed that his line, not a later resurvey, is the legal boundary.
2. The meridian. The 1863 act that split Arizona Territory from New Mexico Territory put the line at the 32nd meridian west of Washington. At the time, American maps measured longitude from a meridian through the old Naval Observatory in Washington, D.C., at about 77°03′ W of Greenwich. According to NOAA's National Geodetic Survey, eleven western states' boundaries were written against that Washington meridian; the United States did not settle on Greenwich until 1912.
3. The 1875 corner. In 1875 the General Land Office hired Chandler Robbins to survey the Arizona–New Mexico line north from the Mexican border to the 37th parallel. He worked from the position of Ship Rock determined a year earlier by Lt. George Wheeler's survey, and he set a sandstone shaft where his meridian met Darling's parallel.
4. The other two lines. Later surveys ran the Colorado–Utah and Arizona–Utah lines from that same point, which is why all four states share it.

The marker has been rebuilt several times. NGS dates the current monument complex to 1992. Rebuilding the marker did not change the legal corner, which is the point the original survey established and the states accepted.

No. The monument marks the legal corner of the four states, and it is about as close to the intended spot as 1875 surveying allowed.

The myth started in April 2009, when news reports said the monument was about 2.5 miles west of where it should be and attributed that to the National Geodetic Survey. NGS published a response the next month saying it had made no such claim. The 2.5-mile number comes from measuring against the wrong prime meridian: it is roughly the distance from the monument to 109° W measured from Greenwich. Congress never used Greenwich. It specified 32° west of Washington, which Robbins himself converted to 109°02′59.25″ W of Greenwich in an 1875 letter.

Measured against the line Congress actually described, the monument is a few hundred yards off, not miles. NGS puts the intended location "about 1800 feet, or less" west of the monument, and says the exact figure is uncertain because the geodetic reference frames of 1875 differ from today's. Our own arithmetic with today's coordinates (the drawing above) gives about 1,350 ft along the 37th parallel, the same order of magnitude.

Even that gap does not matter legally. Once a boundary survey is accepted, the physical monuments define the line, not the numbers in the statute. NGS sums it up as "monuments rule". The Supreme Court applied that rule to this exact boundary system in *New Mexico v. Colorado* (1925): New Mexico wanted a 1903 resurvey of the 37th parallel adopted, and the Court held that Darling's 1868 line, accepted for decades, was the boundary. The Four Corners Monument is therefore exactly where the four states meet, by definition.

Yes. The four quadrants of the monument plaza are in four different states, so a person can put a hand or foot in each, and that is what most visitors line up to do.

A phone will not always agree. Consumer GPS is typically good to within a few meters outdoors, and a few meters is enough to put you on the wrong side of a line you are standing on. Most map apps also draw boundaries from simplified data. If you open What State Am I In at the monument, it reports one state plus the distance to the nearest state line, and that distance will be close to zero. Our boundaries are the Census Bureau's generalized 1:10,000,000 cartographic files, so near any border the honest answer is "on the line", not a specific quadrant.

The same applies to counties. Four counties meet at the plaza, and What County Am I In shows the nearest county line for the same reason. For a coordinate you already have, such as a photo's geotag, the coordinates to state converter runs the same check.

The monument is a Navajo tribal park, so the Navajo Nation, not the National Park Service, sets the rules, fees and hours.

• Hours. At the time of writing, Navajo Nation Parks & Recreation lists seasonal hours that open at 8:00 a.m. and close between 5:00 p.m. (October to late March) and 8:00 p.m. (late May to mid-August). The park closes on New Year's Day, Thanksgiving and the day after, Christmas, and other Navajo Nation holidays.
• Fees. There is a per-person entry fee. Amounts and accepted payment methods change, and federal park passes are a separate system, so check the official park page before you go.
• Time zones. The Navajo Nation observes daylight saving time, while the rest of Arizona does not. In summer, Arizona clocks outside the reservation can be an hour behind the park, Colorado, New Mexico and Utah. What Time Zone Am I In shows which offset your current position uses.
• Services. The site has vendor booths run by Navajo artisans, but it is a long way from full services. The park lists a trading post with groceries and gas about 6.5 miles away.

Because hours and fees are set by the tribal park and can change at short notice, treat any third-party listing, including this one, as a starting point and confirm on navajonationparks.org.

For printing or classroom use, each of the four states has a free outline map with county lines:

• Blank map of Arizona and Arizona counties (Apache County is the corner county)
• Blank map of Colorado and Colorado counties (Montezuma County)
• Blank map of New Mexico and New Mexico counties (San Juan County)
• Blank map of Utah and Utah counties (San Juan County)

The county pages list every county with its seat, population and area, which makes it easy to compare the corner counties. Apache County, Arizona, for example, is far larger than Rhode Island and Delaware combined, a reminder that the Four Corners counties are among the biggest and least densely settled in the country.