Sheri Venditti wrote: ..."my GGF was born in Slonim ca. 1876. The same paperwork shows his wife was born in "Kafkas, Russia" and a later document shows a son born in Baki, Russia in 1901." and asks for help identifying these places, as she can't find any near Slonim.
Here's a thought: maybe the wife wasn't >from near Slonim, and maybe they didn't live anywhere near there when their son was born. My best guess is that the wife was >from the Caucases region of Russia and that Baki = Baku.
(Kafkas in Russian = Caucases; Caucasia is a region located at the border of Europe and Asia, situated between the Black Sea and the Caspian Sea and occupied now mostly by Russia, Georgia, Azerbaijan, and Armenia. At that time, the Black Sea city of Baku (now in Azerbaijan) was part of Russia/Ukraine, and a major target of Jewish immigration >from Belarus.)
To put it all together, maybe your GGF moved >from Slonim to Baku as a young man, married a woman already there, and lived there when he was 25 and their son was born in 1901. I have known family who made a similar migration - a brother of my GGF, family originally >from Zembin, moved to Vitebsk and later (circa 1890) to Baku; at least six of his children were born there 1896 - 1908, and the family remained there until after the 1917 revolution. This man chose to move to Baku (at about the same time his brother, my GGF, came to the USA) because his wife's brothers had already made the same move and were prospering there.
Baku surnames in family: Klionsky, Abezgauz/Abeshaus, Bobod, Beilin