Resurvey of the 37th Parallel

Looking West on US 285 on the Colorado-New Mexico border between Antonito CO and Tres Piedras NM

Looking West on US 285 on the Colorado-New Mexico border between Antonito CO and Tres Piedras NM

US state borders

US state borders

The 37th Parallel. Across the middle of the US lies a 1209 mile long borderline, the longest straight line on the US map (not counting the US-Canada border, of course). It’s a vast strip extending from the verdant east to the arid west, now populated by oil and gas wells, pivot irrigators, cattle, few people, and a couple of dramatic landmarks. What’s noteworthy is the graphic boldness of the line itself, at least for anyone staring at the US map. So… why now should we bother with this line to nowhere?

Purpose. The intention here is to travel along this line, reflecting on the mid-nineteenth century politics that created it while looking at the landscape that presents itself today. The elegant and powerful line, as perceived then, is hard to imagine when gazing at the extensive prairies and deserts upon which it was placed. The line was difficult as well for the surveyors charged with documenting its location. We’ll take a look at the challenge of reconciling the abstract concept of the latitude line with establishing surveyors’ benchmarks on the landscape. The borders, as we’ll come to see, only occasionally coincide with the 37th parallel.

Origin of the line. The line runs between Nevada and Missouri, separating Arizona from Utah, Colorado from New Mexico, and Kansas from Oklahoma. The brainchild of a pre-Civil War Congress, the line divided the vast mid-continent prairie and desert regions into geometric zones with little thought to the area’s inhabitants or geography, about which little was known in Washington.  To facilitate development, the mid-nineteenth century senator-cartographers planned to establish administrative boundaries in the vast– and largely unknown– territory acquired from Mexico in 1848. But drawing boundaries on the map could have threatened the Missouri Compromise; to resolve gridlock over territorial organization and keep the political scales balanced, senators established a long border along the 37th parallel above which territories would be organized as slave-free, while those below the line would permit slavery to be expanded. The line thus represents a continuation of the Missouri Compromise. Once drawn the line was never modified, however, even when the north-south conflict in Congress was mooted by the onset of the Civil War.