What is associated with: 1787 81 yrs old penn snds me 2 cnst cnv im gttng 2 old fr thsstf lol?

Based on the clue '178 feet above sea level on the mississippi river ...', what is the answer? What is associated with: 1781 each state retains its sovereignty freedom and independence? What is associated with: 1783 his britannic majesty acknowledges the said us to be free sovereign and independent? What is associated with: 1783 war over didnt get canada 2day when i signed treaty of this but usa h2s? What is associated with: 1787 law governing the area north of ohio river it became a model for territories entering the… What is associated with: 1787 this state becomes the first to ratify the constitution? What is associated with: 1789 1797? What is associated with: 1789 this document goes into effect?