He was invited by Ruy Barbosa and Lauro Sodré to participate in Brazil's proclamation of the republic. MacDowell declined, declaring himself "defeated, but not convinced". After the fall of the Brazilian empire, MacDowell went to Belém do Pará to deal with personal and family affairs. MacDowell assisted in the elaboration of the state's constitution, and was president of the commission responsible for establishing the boundaries between the state of Pará and the new state of Amazonas.