I have many old pennies why do many of them in the 1950s have a D under the date of the coin are they worth more than one cent?

Pennies (US Cents) with a D mintmark were made in Denver. Common-date wheat-back cents are worth 3 - 5 cents apiece. Of course a very few can sell for thousands of dollars in uncirculated condition. Any copper cent minted between 1909 and 1982 is worth almost 2 cents as scrap metal.