This article exposes the ancient "Nepohualtzitzin" as an important contemporary mathematical tool. The design and development of "Nepohualtzitzin" Ethnomathematics Clubs (NECs) in predominantly Latina/o and low-income schools is also presented. NECs provide informal learning opportunities to develop and strengthen cultural connections to and abilities in mathematics for bicultural-bilingual learners, their parents, and teacher candidates. The formation of NECs is made possible through transnational alliances developed over time between the University of Texas at San Antonio, Secretaría de Educación Pública de México (Ministry of Public Education of Mexico), Coahuiltecan Indian Nation, Aztlán Associates, Danza Azteca Xinachtli, and Tzicatl--Community Development Corporation.