The alphamegalog of South American cities lists the largest city in the continent of South America for each letter of the alphabet. In this case, ‘largest’ is based on population within the city proper.

Arequipa, Peru
Bogata, Colombia
Caracas, Venezuela
Duque de Caxias, Brazil
El Alto, Bolivia
Fortaleza, Brazil
Guayaquil, Ecuador
Huancayo, Peru
Ibague, Colombia
Joao Pessoa, Brazil
Kavanayen, Venezuela
Lima, Peru
Medellin, Colombia
Natal, Brazil
Osasco, Brazil
Porto Alegre, Brazil
Quito, Ecuador
Rio de Janeiro, Brazil
Sao Paulo, Brazil
Terasina, Brazil
Uberlandia, Brazil
Valencia, Venezuela
Wilde, Argentina
Xanxere, Brazil
Yopal, Colombia
Zipaquira, Colombia