Washington (IL) - Adams - Jefferson

My hometown, Washington IL, was founded in 1825. It celebrated its one-year anniversary on July 4th, 1826, the 50th for the Declaration of Independence. Per local lore, John Adams and Thomas Jefferson were both invited to attend the celebration ceremonies in the new town named in honor of their fellow founding father. Both declined due to poor health and knowing now that they would pass on July 4th, it was a wise decision. Both wrote letters, one wrote a toast to be read at the festivities. Locals have lost track of these documents. I wonder if they made it back to the other Washington (DC). I'd love to find out. Any advice on where to search