Record Atlas
5 eras · 1500–2026 · 2 places

The Sonora-Arizona border — the Gadsden line

San Luis Río Colorado, San Luis, Sonoyta. Which empire held this ground in which years — and, the part that matters, which archive that means.

Whose archive this ground was

YearsWho held itWhose archive that means
1500–1848 Sonora (Spanish, then Mexican) Archivo General de la Nación (México) · FamilySearch
1848–1854 Mexico — an unsettled border Archivo General de la Nación (México) · FamilySearch

The Treaty of Guadalupe Hidalgo ended the Mexican-American War but left the border unsettled, including the Mesilla Valley.
1854–1863 Mexico (Sonora) and the United States (New Mexico Territory) National Archives Catalog (NARA) · Archivo General de la Nación (México) · FamilySearch

James Gadsden and Santa Anna signed the treaty on 30 or 31 December 1853; the Senate approved it on 25 April 1854 and it took effect on 8 June 1854 (30 June by another account). The United States gained about 29,640 square miles of southern Arizona and south-western New Mexico for $10 million.
1863–1912 Arizona Territory and Sonora National Archives Catalog (NARA) · Archivo General de la Nación (México) · FamilySearch

Arizona Territory was created in 1863 from the western half of New Mexico Territory. The Southern Pacific Railroad reached Yuma in 1877.
1912–2026 Arizona (United States) and Sonora (Mexico) National Archives Catalog (NARA) · Archivo General de la Nación (México) · Mi Registro Civil · FamilySearch

Arizona became a state on 14 February 1912. The border follows the Colorado River on part of its course, so San Luis, Arizona, and San Luis Río Colorado are in different countries.

The rings are approximate — deliberately. They exist to shade which filing system a place fell under, not to adjudicate a border. A place near a ring's edge should be checked against both neighbours.

See the whole span, 1500–2026, on the map →

The map takes a range, and a range that crosses one of the rows above is where records get lost: the family never moved, and the archive on the far side of the handover will tell you it holds nothing.

2 places on this ground

69 FamilySearch collections reach this ground

Ranked with the regional ones first — a collection for a province is usually a better lead than a national index, though the national index is often where a name is actually written down. A free account opens the images.

…and 9 more.

All record regions · The map