This is my Grandmother and her sister's son. I'm guessing that the sister, her husband and the son and his family went to Washington D.C. to visit my Grandmother's brother who lived in D.C. or maybe just the nephew and his family took my Grandmother to D.C.
I'm guessing this as the date is August 1957 before my time.
Look at the shoes my Grandmother is wearing. My feet would kill me if I walked around on vacation in heels!
The next two pictures are my Grandmother, with nephew, wife and daughter.