First of all, Russian-Poland refers to a large part of the Pale of Settlement that operated under the Tzar for much of the 19th century.
The boundaries of the Russian Empire changed over time. Please refer to the(UK)Times Atlas of European History for maps showing the changes. There are also maps online.
The best way to find out where your ancestor came from is to look at the following records on the UK National Archives website, Ancestry or FindMyPast:
- UK Naturalisation records at the National Archives or on Ancestry. I found these for three out of four sets of my great grandparents, who all naturalised in the 1890s, having been in UK for 30 years.
- Using Census Records. My 4th set of great grandparents were not naturalised but I finally found their place of origin in the 1911 Census (it had not been mentioned in the 1871, 1881, 1891 or 1901 censuses). I also confirmed this through DNA testing with a 3rd cousin in USA who had a detailed paper trail, and information about a change of surname, reverting back to a patronym. This was also confirmed by JRI Poland. All the evidence matched up.
Jill Whitehead, Surrey, England.