Women in Costumes

It's hard to say what's a costume versus what are normal, everyday clothes.  I define a costume as anything you wouldn't wear to Walmart.  For example, the lady below is not dressed properly to go to Walmart.

Instead, she went to Simmon's Studio and had this picture taken.  I don't know why.

These women from the Alpha Sigma Alpha Sorority are also wearing costumes.  

I sent this picture to the Alpha Sigma Alpha Headquarters and asked them if they knew anything about this event.  I never heard back from them.

Do you have any information about either of these pictures?