United States rule over the Philippines following the Spanish-American War, first as a military/insular government, then (from 1935) as the semi-autonomous Commonwealth of the Philippines preparing for independence.
Independence granted 4 July 1946 per the Tydings-McDuffie Act's ten-year Commonwealth timetable, becoming the modern Republic of the Philippines (already canonical, id: philippines).
The atlas holds 4 border frames for American Philippines (Insular Government / Commonwealth) — the shape you scrub through changes in 1898 · 1915 · 1934 · 1945.
Verified via Open Library (already used elsewhere in canonical dataset's own Philippines reading list); Pulitzer-winning account of the entire American colonial period.
Verified via Open Library (author + title + year match); scholarly analysis of Insular Government administration.