They were signing a petition to establish the 'Columbia Territory'.
I believe the the answer is her biography's
A.D means in our time (Anno Domini, the year of our lord) and B.C means Before Christ - these two and the other mentioned words are used to B. refer to periods of time.
Early humans eventually formed hunter-gatherer societies so catching food and cooking it could be split evenly between the people, and so everyone could get food properly, all the while sharing with eachother and looking out for eachother. Being in groups made it easier to catch more food, because they could take out more than they could together than with only one person. Forming these societies made things much more easy and efficient for them.
