Treaty citizens became invested in a U.S. political system where the federal, state, and local governments initially catered to them in their preferred language, Spanish. This chapter briefly traces the arc of Spanish as a language of citizenship. States and territories had the power to determine the parameters of individuals participating in elections, in courts, as jurors, and by officials in federal and state government positions. California, Colorado, and Arizona’s concessions to Spanish as a language of participation for citizenship began with official recognition, but never became fully bilingual regions. New Mexico, on the other hand, used Spanish as an important part of the electoral process and the courts. Treaty citizens in New Mexico became invested in the territory's elected and appointed positions. The political power meant Spanish had a centralrole in territorial politics. Treaty citizens participated and engaged in a U.S. political system in Spanish in elections, in the courts, and in juries, which forces a reassessment of American citizenship in the last half of the 19th century.