Cindy,
I have not found too much on the Plumhoff's but will definitely share what I have. Please email me at jcr8on1 at cox.net. I don't know how much information you have on Heinrich (Henry) & Sophie Plumhoff Rosenberg but am willing to share that as well. If you have never seen a photo of them, remind me via email as I have a nice picture of them in their later years. I read several other postings regarding the German Jews and although Rosenberg sounds Jewish to me, Henry was instrumental in starting the German Evangelical Church in Martin County MN before they left for ND which leads me to believe they were not of the Jewish faith. Have you ever found his death certficiate? I believe he died in North Dakota as his body was sent back to MN for burial via train.
Jackie Swink Creighton