American mahjong is not a simplified form of Chinese mahjong
It is a different game that happens to use the same family of tiles. If you learned riichi, Hong Kong or Sichuan rules first, almost every instinct you built will be wrong at an American table.
American mahjong grew out of the mahjong craze that swept the United States in the 1920s, after Joseph Park Babcock published a simplified rule set for American buyers. Players kept inventing hands, and by the mid-1930s the game had drifted a long way from its Chinese roots.
In 1937 the National Mah Jongg League (NMJL) was founded in New York City to standardize the rules. Its defining invention was the annual card: a printed sheet, sold each year, that lists every legal winning hand for that year. Nothing off the card counts. That single decision makes American mahjong a game that genuinely changes every spring.
Today it is a social institution across the United States and Canada — country clubs, synagogues, community centers and weekly home games. Tournaments run year-round under the Standardized National Mah Jongg Tournament Rules, and the season culminates in the National Mah Jongg Convention held each March.
There is a card, and it changes every year
You do not build “four melds and a pair.” You build one exact line printed on the current year's NMJL card — tile identities, group sizes, suit relationships and concealed-or-exposed status all specified. Last year's card is not valid this year.
The Charleston is mandatory
Before anyone discards, players pass three unwanted tiles to each neighbor in a fixed sequence: right, then across, then left. No other mahjong variant opens with a structured tile exchange.
Eight jokers, with their own rules
Jokers are wild — but only inside groups of three or more. They can never stand in for a required single tile or a pair, and they may never be passed during the Charleston.
How the three main variants compare
| Feature | American (NMJL) | Chinese / Hong Kong | Japanese (riichi) |
|---|---|---|---|
| Tiles in the set | 152 — adds 8 flowers and 8 jokers | 144 — includes 8 bonus flowers and seasons | 136 — plus red fives in some rules |
| What a winning hand is | An exact line on the current annual card | Four melds plus a pair, scored by fan | Four melds plus a pair, scored by han and fu |
| Sequences (chows) | No — groups are identical tiles: pungs, kongs, quints, sextets | Yes | Yes |
| Opening tile exchange | Required — the Charleston | None | None |
| Wild tiles | 8 jokers, tightly restricted | None by default | None |
| Tiles held | On a rack, exposed groups on top | In hand | In hand |
| Scoring | Read the printed value off the card | Count fan | Count han and fu, then look it up |
Variant details vary by region and by house. This table describes the standard forms as commonly played.