Maize domestication (Zea mays ssp. mays L.) resulted in a wide diversity of native landraces that represent an invaluable source of genetic information for exploring natural variation and genome evolution. We sequenced de novo the approximately 2-gigabase genome of the Mexican landrace Palomero Toluqueño (Palomero) and compared its features to those of the modern inbred line B73. We revealed differences concordant with its ancient origin and identified chromosomal regions of low nucleotide variability that contain domestication genes involved in heavy-metal detoxification. Our results indicate that environmental changes were important selective forces acting on maize domestication.