What is the oldest penny in circulation?

the 1961 penny

Correction

No person or agency keeps track of what coins are in circulation. Because cents have been made of bronze or have been copper-colored for about 150 years and have had the Lincoln design on the front for a century, sometimes older coins aren't recognized as such and continue to circulate until a collector or other curious person finds them. It's still possible to find cents from the 1930s in circulation but extremely infrequently. Later date wheat cents turn up somewhat more often, but even these are disappearing because they have a different reverse design, which means that the vast majority of cents in change are dated 1959 and later, with most of those dating from the late 1970s and newer years.