20,000–30,000 total settler deaths over nearly three centuries, with a commonly cited atrocity-specific tally of around 7,000–9,000—draw from historical compilations focusing on documented incidents of violence. No single definitive count exists due to incomplete records, but here are the key sources:
William M. Osborn, The Wild Frontier: Atrocities During the American-Indian War from Jamestown Colony to Wounded Knee (2000): Osborn compiled a chronological list of documented atrocities from 1511–1890. He tallied 9,156 deaths attributed to Native American actions (primarily settlers and civilians) and 7,193 to settler/European actions. This is one of the most comprehensive atrocity-focused counts and supports the lower end of broader estimates (around 7,000–9,000 for settler deaths from direct violence/atrocities).
Gregory F. Michno, Encyclopedia of Indian Wars: Western Battles and Skirmishes, 1850–1890 (2003): Focusing on the later Indian Wars period (a major phase of conflict), Michno documented ~675 engagements, with total casualties of ~21,586 (including killed, wounded, and captured). Of these, ~6,596 were non-Native (military and civilians), implying several thousand settler/military deaths in this era alone. This contributes to higher overall estimates when combined with earlier colonial conflicts.
U.S. Census Bureau (1894) estimate (cited in histories of the American Indian Wars): For 1789–1891, ~5,000 white deaths from warfare (plus ~8,500 Native deaths), with broader violent deaths estimated at ~28,500 whites over longer periods in some compilations.
Broader ranges (up to 20,000–30,000) incorporate undocumented raids, military deaths, and extrapolations across all conflicts, as noted in summaries on sites like Wikipedia's American Indian Wars page.