Now I know exactly when Sam died and where he was buried. His second wife, Margaret, didn't give any details such as birth date or home town when providing info for the death cert, unfortunately, but I'm not surprised about that.
What was a surprise is that he's buried in the same cemetery as his first wife, which is the same cemetery where my paternal grandparents are buried. Is it a coincidence? Well, I have a plot plan for where my paternal ancestors are buried and Uncle Sam's name doesn't appear on it. I'll check with the cemetery for more about the area in which Uncle Sam is buried. Maybe other relatives are buried nearby?
What I learned: Pay attention to the stories that relatives tell. One cousin said she this relative had a heart attack while mowing his lawn on a hot summer day--and it turns out she was right, he died in June. Another cousin was able to narrow down the range of years for when my great-uncle died, and he was right. Otherwise it would have been impossible for me to take an educated guess. I would have spent much more time and money searching for Great-Uncle Sam.
2022 update fixed links.