Halloween (Primary Sources)

Halloween costumes from the first half of the 20th century were terrifying. Drawing on the holiday's pagan and Christian roots -- as a night to ward off evil spirits or reconcile with death, respectively -- people often opted for more morbid, serious costumes than the pop culture-inspired ones of today. Wearing ghoulish costumes -- not horror-inspired like today's, but plain frightful -- was an essential part of it. 

Hiding behind their costumes, villagers often played pranks on one another, but blamed the spirits. Masks and cover-ups came to be seen as means to get away with things. That's continued throughout Halloween's evolution. People in rural America really embraced its pagan roots, and the idea of it as a dark occasion, centered around death. They wore scary, frightening get-ups, which were made at home with whatever was on hand: sheets, makeup, improvised masks. Anonymity was a big part of the costumes. The whole point of dressing up was to be completely in disguise. 

The 1920s and 1930s, saw the emergence of costumes influenced by pop culture, alongside the first major costume manufacturing companies. After World War II, as TV brought pop culture into family homes, American Halloween costumes increasingly took after superheroes, comic characters and entertainment figures. They also became increasingly store-bought. 

source: https://www.cnn.com/style/article/history-of-halloween-costumes/