Who formed the Triple Alliance in Mexico and which territories did it dominate?

The largest Mesoamerican alliance was formed by the lordships of Tlacopan, Texcoco, and Tenochtitlan, which united in the 15th century to impose their hegemony over the Valley of Mexico against the lordship of Azcapotzalco.

Who formed the Triple Alliance in Mexico and which territories did it dominate?
Codex Osuna,f 34r, detail. The towns of the Triple Alliance. Representation of the towns that made up the triple alliance Texcoco, Mexico, and Tacuba at the arrival of the conquistadors. Image: UNAM