1919 is so common because after World War I (1914-1918) the US government wanted to be sure there was enough money in circulation so that commerce was not impeded. They really ramped up penny production, more than any other denomination, because many people hoarded coins during the war.
I think you will find that of the 3 most common 'teen' years (1917, 1918, &1919) the 'D' mint mark is the most desirable (even more desirable than the 'S' mint mark for those years.
A problem free 'D' mint in these years in any condition has a definite higher value than 'S' mm. Usually the 'S' mint is the most desirable, but for those dates you got a really nice find if you can pick up the 'D' mint in good condition from rolls or bags.