Obviously, this picture was taken on a Monday. The scene is the tenement backyard at Park Avenue and 107th Street in New York, probably in the year 1900.
Setting up these clotheslines was not a trivial task, especially on the higher floors. A man would come around calling out "I climb poles!" and for about 25 cents he'd climb up and run the rope out over the pulleys. He also sold rope and pulleys, but if you'd planned ahead and bought them from the hardware store, you could save a few cents.
Notice the train track at the bottom of the photo--I'm guessing the whites were whiter at the far end of the block. Just on the other side of the tracks is the building where baseball player Lou Gehrig grew up, a few years after this picture was taken.
I suggest viewing this image as large as possible, so you can peep into the windows.