This chapter focuses on the linguistic input to American varieties of Spanish. It first explains the Andalucista model, the most widely accepted explanation for the nature of American Spanish, which claims that it is, in essence, an offspring of Andalusian Spanish. Data in support of this argument have mostly been phonological and demographic in nature. Critics of this model, however, argue that neither phonetic features nor speaker numbers provide convincing evidence to uphold the model, and that American varieties differ substantially among each other. Rather, multiple factors appear to have played a role in the evolution of a colonial koine that evolved into further varieties in different regions of the Americas. The chapter shows that it is relevant to consider at what point in history certain changes occurred, since certain distinguishing phonetic features of American Spanish may in fact have evolved independently and at a later point in time but in accordance with processes of language change from Castillian to Andalusian Spanish, thus continuing a process of language change that had been initiated long before Spanish was taken to America.