In Eastern Galicia (present-day Western Ukraine and parts of South-Eastern Poland) ethnic and national identity correlated with religion, with mainly Roman Catholics identifying as Poles and Greek Catholics usually as Ukrainians (there were even families in which siblings had different ethnic / national identities). Here is a map of Polish and Ukrainian (including Rusyns / Ruthenians) areas in 1900:



Political situation in the late 16th century:



Borders of I RP in year 1772 and of II RP between the World Wars:



This is a very good book (below I post Table 4.45 from this book):

https://books.google.pl/books/about/...gC&redir_esc=y