On March 21st, 2015, these men and women gathered for a hike of Rock Creek Park. The weather must have been rather brisk that day.
This photo is from the Willard R. Ross Postcard Collection at the DC Public Library, digitized and available online at DigDC.DCLibrary.org.
According to the library, Ross was born in 1860 and moved to DC around 1910. He became a postcard photographer specializing in “hometown” views. Ross concentrated mostly on images of buildings and monuments, but he also enjoyed photographing the Wanderlusters, a coed hiking club.