1788-1792 U.S. Postage Rates Change: From Pennyweights & (dwt) Grams (gr) of Silver to Federal Cents

1788-1792 Postage Rates, Confederation to Statehood Transition: From Silver weight Postage Rates, Pennyweights (dwt) & Grams (gr), to Federal U.S. Cents

1788 Congress by Resolution of October 20, 1787, reduced the rates of 1782 effective April 5, 1788, “as nearly 25 percentum as will consist with the mode of calculating pennyweight (dwt)* and grams (gr) of silver, in order to reduce them to the currencies of the several states,” as follows:

Miles Inland
To 60            1 dwt
60 to 100        1 dwt, 8 gr
100 to 200        2 dwt
200 to 300         2 dwt, 16 gr
300 to 400        3 dwt
400 to 500         3 dwt, 8 gr

Each ship Letter:
Add to Inland        Postage at Port
16 gr            16 gr

*This abbreviation for pennyweight “dwt” was derived from “d,” for the Roman denarius, was the abbreviation for a penny and “wt” for weight. A pennyweight is a unit of mass equal to 24 grains, 1⁄20 of a troy ounce, 1⁄240 of a troy pound, approximately 0.054857 avoirdupois ounce and exactly 1.55517384 grams.

1 pennyweight = 24 grains
= 1⁄20 Troy ounce
= 1⁄240 Troy pound
= 1.55517384 grams

1 Grain of Silver = 1/24 Penny Weight

As of this writing in January, 2024, with silver in range of $32/troy ounce, the most inexpensive rate to send a letter up to sixty miles at 1 pennyweight would be roughly $1.60 worth of silver today. 

Statehood Period
Act of February 20, 1792, Effective June 1, 1792
Not over 30 miles    6 cents
30 to 60 miles        8 cents
60 to 100 miles    10 cents
100 to 150 miles    12 ½ cents
150 to 200 miles    15 cents
200 to 250 miles    17 cents
250 to 350 miles    20 cents
350 to 450 miles    22 cents
Over 450 miles    25 cents

Act of March 2, 1799 (ASCC assumes effective same date)
Not over 40 miles    8 cents
40 to 90 miles        10 cents
90 to 150 miles    12 ½ cents
150 to 300 miles    17 cents
300 to 500 miles    20 cents
Over 500 miles    25 cents