Stieglitz (1864-1946) was an American photographer and art promoter. He is best known for his NYC galleries, "Camera Work" - a photographic journal, and for promoting photography as an art form.
"Winter, Fifth Avenue" was taken in the early 1890s and over the years there have been many different versions. Stieglitz himself exhibited different versions as examples of the effect of cropping and cloning. The version shown below was published in the October 1905 issue of "Camera Work" using the photogravure (intaglio printmaking) technique.


Stieglitz did not have any issues with cropping and/or altering the original image, although I understand some of his contemporaries did...

Thanks for looking,
Casey
Have a look at the following video as an introduction... (running time 1 hour 27 minutes)
One famously altered photo is John Filo's Pulitzer Prize winning image from the May 4, 1970 shootings at Kent State University in Ohio (USA).


For any not familiar with the above photography, the incident involved the shooting of four unarmed college students by the Ohio National Guard during an anti war protest.
There are just as many examples where the original unaltered photograph is more appropriate... and indeed I can accept either way regarding cloning for non-PJ photographs...
Casey