94% sureThese words were traced back to where they first appeared. That source is listed below.
What turned up
38th NAWSA Convention, Baltimore, 15 February 1906 (Anthony's last public address)
Sources checked
loc.govChecked using claude-sonnet-5, 20 August 2026
nps.govChecked using claude-sonnet-5, 21 August 2026NPS history article confirms 'Failure is impossible!' as Anthony's concluding words, though dated to her Jan 10, 1906 birthday celebration, not the Feb 15 NAWSA convention — likely said at both closely-spaced 1906 events.