The Duchy of Acre was carved out of the old Kingdom of Jerusalem by Richard Courleon, Prince of Edessa, as he raced to the rescue of Baldwin the Leper King in Caesarea. Richard claimed the coast from Tyre to Carmel as a fief of England. When Richard became Richard I, King of England, he passed the Duchy to his youngest son Baldwin, and to Baldwin's heirs.
As a fief of England, the government of Acre has been remarkably stable for the past 380 years. It's biggest changes came about as a result of the reformation, when Acre became the only Protestant land in Outremer. The Knights of St Thomas of Acre, once a Catholic order, but now Protestant, are headquartered in the northernmost city of Tyre.
The Duchy of Acre is small, but rich - considerably richer than England, in fact. It is the terminus of the silk trade from China, and the main port for Damascus, further inland. The revenues of the Duchy are enormous, and the Duchy imports most of the food needed to feed it's huge population from Edessa, Cyprus, and Armenia. The Dukes of Acre brought in steelworkers from Damascus very early on, becoming the arsenal of Outremer. In the last century, gunsmiths have begun to rival blade-smiths for both honor and money.
Acre, Tyre, and Haifa are all seaports, and the wealth of Damascus and points east flow through these ports. Relationships with the Emirs of Damascus are usually very good, though relations with the rest of Outremer vary. Most states are jealous of the wealth of Acre, but all want the fruits of her foundries.
Here's a map of the Duchy of Acre:
And here is the current Duke and Duchess of Acre: