Post-mortem photography sprung up in the mid 1840's and was alternately known either as memorial portraiture or mourning portraits. These photos hold a special place in our history, because they often represented the only visual rememberance of the departed. Photography was so rare and expensive then that many of the photos from the 1840's until the 1870's were mourning photos.
Memorial portraits were very common in the 19th century when death occurred at home and was quite an ordinary part of family life. That said, the passing itself often promted the family members to take quick action, quickly beckoning or heading in a buggy to the nearest photographer. These became precious keepsakes for the family and lasted those many years after the person had passed. The practice peaked at the end of the 19th century as standard snapshot photography took over and people often had more than enough photos of the person living, and it became an accepted understanding that it was rude to photograph the dead if you had a memory of their living.