Finely chop rhubarb. Do not peel. Place in a large pot. Add water and bring to a boil. Reduce heat and simmer 2 minutes or until rhubarb is soft. MEASURE 4 1/2 CUPS rhubarb and discard any remaining rhubarb or save for another use.
Place the 4 1/2 cups rhubarb back into the pot, stir in the pectin, and add the butter. Bring to a full rolling boil on high heat, stirring constantly. Quickly stir in all the sugar and the cinnamon. Return to a full rolling boil. Boil for exactly 1 full minute stirring constantly.
Remove from heat. Skim foam. Can add a few drops of red food coloring if desired. Ladle quickly into sterilized jars, leaving 1/4 inch headspace. Wipe rims. put caps on. Process in a water-bath canner for 10 minutes.