Genealogical Treasure Trove

A relative of mine recently died in Florida. While rummaging through her things, her husband found a letter written by my late father when he was a Master Sergeant in the US Army.
My dad was born in Germany and managed to get out during the early stages of World War II. His parents applied for visas too, but never got out.
In this letter, dad talks about searching for his parents' whereabouts by hitchiking to a concentration camp where they once had been.
Ultimately, he would find out his father was gassed at Auschwitz, but his mother survived, moved to Florida and lived to the ripe old age of 99.
Anyway, in this letter, dad mentions three other surnames apparently related to the Ries family through marriage.
What valuable information this was! Because of it, I was able to trace genealogy on my dad's side back to 1798. What's sad is the great number of relatives who died at the hands of the Nazis at Sobibor and Auschwitz concentration camps. There are 12 of them in this group, plus my grandfather and other members of his immediate family.
Todat, we have a small family, but this gives me a glimpse of how large we once were. I was also able to find photos of gravestones belonging to Henriette Ries Norden (9/6/1847-8/12/1918) and Flora Ries van Hasselt (2/1/1848-6/9/1916). Flora was particular prolific. She gave birth to six kids in eight years. I don't envy her and her husband Elias.
Prior to my dad's letter, I knew little about our family pre-WWII. Now, I learn more each time I do research.