In this study we analyze phonic and morphological features present in 40 letters written in Spanish. These letters date between 1883 and 1937 and their authors were workers of the Chilean nitrate fields, a mining enclave in northern Chile. The features present in these letters reveal the vernacular speech of these workers. This is characterized by a number of meridionalisms (weakening and neutralization of consonants) and the presence of archaisms and other nonstandard features, probably indicative of a process of inter-dialectal leveling linked to the immigration of people mainly from central and southern Chile. Furthermore, we call attention to the abundance of hypercorrections, which we interpret as the effect of a phonetically conservative normative linguistic model, of peninsular imprint.