Here’s a cool photo of a car crossing a part of Rock Creek in the 1920s.
Source: Library of Congress
And here is, what appears to be, the same location in Rock Creek, this time being crossed by riders on horseback.
Revisiting Rock Creek: A Photo Comparison of a Car Crossing and Horseback Riders
pretty sure this is the “Milkhouse Ford”
Absolutely the Milkhouse Ford, sometimes just called Rock Creek Ford. Indeed, it’s the only such ford on the creek (that is, regularly used by horses and vehicles) in DC. An old road crossed the creek at this ford, called variously the Milkhouse Ford Road and Rock Creek Ford Road. A fossil remnant of this road still exists, with the same name and a few homes and addresses on it, between the Park and Georgia Avenue.