A few nights ago, I watched a documentary on PBS on the rescue of the Willie and Martin Handcart Companies in 1856. Some of my family were mormon pioneers, and so I was somewhat interested.
After the show, I decided to see if I had any relatives that were in the ill-fated companies. An uncle of mine had mentioned once that we had "handcart pioneers" in our past. It turns out he was entirely wrong. Our common mormon ancestors arrived in Salt Lake in 1850, 1852, and 1864 - completely missing the handcarts from 1855-1860. They travelled mostly by wagon.
Anyhow, it was interesting in that I never realized just how Mormon my family really was. For example, my great great great grandma was born in Nauvoo, IL - and my great great great great grandpa helped build the temple there. By the time I was born, I guess my chunk of the family had fallen mostly away from the church.
What was most interesting of all was the fact that nearly all of my ancestors had RIDICULOUS NUMBERS of kids. My great great grandpa, for example, had 13 total children over his lifetime - and had 10 of those after the age of 41. Pretty incredible. Math wise, if every generation had that many children - think how big the family would be by the time it reached my generation.
Great great grandpa is 4 generations back. So:
4 back. Great great grandpa has 13 kids. Next generation = 13
3 back. Great grandpa and kin have 13 kids. Next generation = 169
2 back. Grandpa and kin have 13 kids. Next generation = 2,197
1 back. Father and kin have 13 kids. My generation = 28,561
So in just 4 generations, you can have almost 30,000 people that call you "common ancestor." That's in a perfect world of course, where no one ever dies or goes sterile. So I guess you don't just have to do something great to be historically meaningful - you can also go by the "have a ton of babies" route.