In the 1921 census (I can't give full details) John Witte gives his birthplace as Pomerania, Germany. In the 1891 census I read his birthplace as Stralsund, Prussia. Stralsund is indeed in Pomerania and was part of Prussia 1815-1918, becoming part of Germany at the end of WWI.
Added: Apologies Neal1961 I see that you already spotted Stralsund.