El Día de los Muertos/Day of the Dead/All Souls Day has its roots in the Aztec and Maya traditions of Mexico and is thousands of years old.
It has become more & more recognized and celebrated here in the greater American West in recent years. The Day of the Dead as it is celebrated in central and southern Mexico is an incredible amalgamation of native and Catholic beliefs, and honors departed members of the family. As the time of year when the veil between the worlds is the thinnest, it is believed that the departed actually come back, returning to visit their grave sites and the scenes of their lives.
One of the ways that Mexicans cope with loss is to view the concept of death in an almost playful manner. Markets are filled with candy skulls (complete with names) and statues and depictions of calacas (skeletons) engaged in everyday acts like playing music, celebrating weddings (and funerals!), riding skeleton horses, bikes, and countless other life delights.
Artists have participated in the long-standing tradition of creating calaveras (skulls) to celebrate this event - often satirizing the events, customs and personalities of the day. The most famous Mexican artist known for this is José Guadalupe Posada.
In the northern frontiers of Mexico and border regions, El Día de los Muertos is more muted but departed family members are honored just the same. Fall is when families of the departed clean grave sites, give them fresh paint, and decorate the graves with flowers--fresh, silk/plastic, and hand-made paper.