This study analyzes the patterns of incorporation of English elements in New Mexican Spanish in the decades following the annexation of New Mexico by the United States as reflected in a corpus of private letters written between 1848 and 1936. The quantitative analysis shows that most types of contact features are infrequent during much of this period, but there is an increase in the presence of English elements in the last decades covered by the corpus. It also shows that semantic and lexical borrowing is much more frequent than structural interference or code-switching. These findings are then correlated with the general sociolinguistic environment of post-annexation Hispanic New Mexico, where bilingualism and language shift to English were much more infrequent than elsewhere in the US Southwest. Attention is also paid to features that pertain exclusively to the written language, and their distribution is explained as a function of the degree of exposure of Hispanic New Mexicans to literacy in English and Spanish.