While making the maps for yesterday’s post about the extent of US federal landownership, I noticed an odd checker-pattern in one part of it. It flowed through northern Nevada and Utah, and then out a ways into southern Wyoming. I did enough work to make sure it wasn’t a coding error on my part, but didn’t pursue it any further. This morning, JP Lien asked me about it on Twitter, and we both took a closer look. Here’s what the pattern looks like close up.

Checkerboard land ownership pattern.

Checkerboard land ownership pattern.

And here it is running through the whole of Nevada:

Public Lands in the State of Nevada.

Public Lands in the State of Nevada.

JP quickly turned up a US Bureau of Reclamation document that explained things. The checkerboard pattern is a fine-grained patchwork of alternating public and private land ownership. It dates back to the 1860s and the construction of the First Transcontinental Railroad:

Land ownership within the Humboldt Sink and Rye Patch Reservoir areas is dominated by a “checkerboard pattern” of alternate privately and publicly held land. This ownership pattern is a result of land grant transfers from the federal government to the Central Pacific Railroad Company in the 1860s. Odd-numbered sections were granted to the railroad in a corridor extending 20 miles on each side. This 40-mile-wide corridor of alternating private and public lands follows the Humboldt River and affects land ownership in the project area.

Here’s a map of the railroad route:

Part of the route of the First Transcontinental Railroad. Central Pacific line (red), Union Pacific line (blue).

Part of the route of the First Transcontinental Railroad. Central Pacific line (red), Union Pacific line (blue).

And why, you might ask, was the railroad going this way? The answer is, as its Wikipedia entry notes, that the Humboldt River, which runs more or less east-to-west through northern Nevada and empties into the Humboldt Sink, is the only natural transportation artery across the Great Basin. The basin is about a half-million square miles of land centered on Nevada and covering the western half of Utah and parts of Orgeon and California. It is a huge, contiguous endorheic watershed, meaning that none of the rivers in it drain to the ocean. The Great Salt Lake is at its eastern end; Lake Tahoe and Pyramid Lake, and Goose Lake are on its western side. Crossing the Great Basin means following the Humboldt River. That’s what overland travelers to the California Gold Rush did in the 1840s; it’s what the First Transcontinental Railroad did in the 1860s; and it’s what Interstate 80 does now. (The routes aren’t quite identical. I-80 was able to blast its way through some obstacles the railroad had to go around.) Between the geography of the region, the division of land grant parcels, and the development of the railroad, the net result is the checkered pattern of land ownership visible in the Federal Land Use Map Layer, much as the curves of the Mississippi, Missouri, and Ohio rivers are visible in county-level maps of the United States.