20 Pesos Sonora Bank

Banco de Sonora was one of the privileged regional banks operating under Mexico's 1897 Ley General de Instituciones de Crédito, which granted select state-chartered institutions the right to issue circulating notes — a right jealously guarded and commercially lucrative. The bank served the northwestern frontier economy, where mining and cross-border trade with Arizona made dollar-denominated commerce a constant competitive pressure on peso notes.

American Bank Note Company held the printing contract throughout the series run, a common arrangement for Mexican regional banks of the Porfiriato period who trusted New York security printers over domestic alternatives. The relationship ended abruptly when revolutionary disruption and the 1913 forced closure of most state banks terminated circulation entirely.