Where Are Your Coins From?

The coins in your pocket tell you where they were minted. The U.S. Mint has assigned a mint mark for each of its four facilities. Every coin minted by the U.S. Mint (except the penny) has a mint mark which identifies the facility the coin was produced in. In this activity, you will be reaching into your pockets to get data to analyze.

Ready:

To learn more about the locations of Mint facilities in the U.S. and the marks that are stamped on each coin to identify the production location, visit the following sites:

By now you should have come across the locations of the active Mints in the United States: Philadelphia, Denver, West Point, and San Francisco. Of these, Philadelphia and Denver are the only two that produce all of the circulating coins in the United States. Philadelphia's mint mark is "P" and Denver's is "D". The only coin that currently does not have a mint mark is the penny produced in Philadelphia.

Set:

For this activity, you will need to bring in a handful of coins (not pennies!) from home. No more than 5 to 10 per person are needed. Before we begin, in groups of four, you will need to agree on an estimate of where more of your coins will be from. Write down your estimate in percentage form (ie. We believe 75% of our coins will be from the Philadelphia Mint.)

Go:

Next, sort your group's coins according to which facility they were produced at. Each group should make a line plot graph showing the number of coins from each facility. Remember from your reading that coins issued in certain years did not have mint marks. You may need to add a column for coins which don't have a mark on them. The type of coin does not matter for this activity.

Sample Line Plot Graph

After you have created your line plot graph, analyze the data:

  1. Where were the majority of coins in your group minted?
  2. What percentage of your coins were minted in Philadelphia? Denver? How did this result relate to your estimate?
  3. Survey other groups to see which Mint facility is represented more often. Do the results surprise you?
  4. Why might the majority of our coins be minted in one location?
  5. What do you think the results of this experiment would be in New York City, Seattle, or Orlando?

If you have extra time, sort the coins according to year or decade to see when the majority of coins in your sample were produced.

  1. When was the oldest coin in your sample produced? The newest?
  2. Write down some differences you see among the same coin produced in different years.