Record Atlas
5 eras · 1803–2026 · 42 places

Montana and Wyoming — Louisiana Purchase and Oregon Country to territories

Billings, Helena, Missoula, Cheyenne, Casper, Laramie. 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
1803–1846 Louisiana Purchase east of the Continental Divide; Oregon Country west of it FamilySearch · National Archives Catalog (NARA)

Wyoming's ground east of the Continental Divide and Montana's east of it were part of the 1803 Louisiana Purchase; ground west of the Divide and north of the 42nd parallel was in the Oregon Country, where Britain and the United States shared access from 1818 until the Oregon Treaty of June 15, 1846. A corner of southwestern Wyoming came to the U.S. in the Mexican Cession of 1848.
1846–1863 Oregon, Washington, Nebraska, Dakota and Utah territories FamilySearch · National Archives Catalog (NARA)

Ground west of the Divide lay in Oregon Territory (1848), then Washington Territory (1853); ground east of it lay in Nebraska Territory and from March 2, 1861 in Dakota Territory, which then included much of present Montana and Wyoming. Records before 1863 therefore sit under those territories.
1863–1868 Idaho Territory, Montana Territory and Dakota Territory FamilySearch · National Archives Catalog (NARA)

Idaho Territory was created on March 3 or 4, 1863 (dated differently by source) out of land that included Dakota's. Montana Territory was organised from Idaho Territory on May 26, 1864 (dated May 28 in one account), and Wyoming Territory followed on July 25, 1868, formed from Dakota, Idaho and Utah territories.
1868–1890 Montana Territory and Wyoming Territory FamilySearch · National Archives Catalog (NARA) · Chronicling America

Wyoming's territorial government was organised on April 17, 1869, and in 1872 the territory had five counties: Albany, Carbon, Laramie, Sweetwater and Uinta. Montana became a state on November 8, 1889, and Wyoming on July 10, 1890.
1890–2026 United States — Montana and Wyoming FamilySearch · National Archives Catalog (NARA) · Chronicling America

Statewide birth and death registration began in Montana in 1907 (practitioners were first required to keep records in 1895) and in Wyoming in 1909, with some earlier county registers in Albany and Laramie counties.

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, 1803–2026, 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.

42 places on this ground

1742 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 1682 more.

All record regions · The map