My personal choice is Ben Franklin's final appeal for passage of the Constitution by the Constitutional Convention. The Convention was divisive and difficult and came near collapse often. Franklin was in his 80s, infirm and gout ridden, exhausted from putting out the fires of dissension and dissatisfaction, and he could barely speak. Delegates had to strain to hear in that hot and contentious place. The importance of this speech is this: If it hadn't worked, there may not be an America. Here's what they heard:
...for having lived long, I have experience many instances of being obliged, by better information or fuller consideration, to change opinions even on important subjects, which I once throught right, but found to be otherwise ... Most men, as indeed most sects in religion, think themselves in possession of all truth, and that wherever others differ from them is so far error ... I agree to this Constitution, with all its faults, if they are such ... I doubt too whether any other convention we can obtain may be able to make a better Constitution, for when you assemble a number of men to have the advantage of their joint wisdom, you inevitably assemble with those men all their prejudices, their passions, their errors of opinion, their local interests, and their selfish views. From such an assembly can a perfect production be expected? It therefore astonishes me, sir, to find this system approaching so near to perfection as it does and I think it will astonish our enemies who are waiting with confidence to hear that our councils are confounded, like those of the builders of Babel and that our states are on the point of separation only to meet thereafter for the purpose of cutting another's throats.
Thus I consent, sir, to this Constitution because I expect no better ... the opinions I have to its errors, I sacrifice to the public good ..."