In 1789, how did the economy of the Mid-Atlantic states differ from the other regions?
The economies of New England, the deep South and the Mid-Atlantic states all involved small farms and towns with small manufactories and merchants, but there were differences. In New England the economy centered on small farming communities, with the larger towns having merchants and manufactories, and some mining operations in the hills. The deep South, of course, was economically tied to small family farms and the large plantations with their cash crops, which before the invention of the cotton gin were largely hemp and tobacco. Cotton became "King" after Eli Whitney's invention made the mass processing of cotton financially feasible.
The Mid-Atlantic states' primary agricultural products were grains (except Virginia, which was the premier Southern plantation state and so grew much hemp and tobacco), and this was much of the basis of the shipping businesses in large towns and cities on the coast. The grain economy of these states had been severely disrupted by the French and Indian War and worse by the Revolution. There were boom prices early in the Revolution, but after the British seized Philadelphia in 1777 Washington's confiscation of millstones (to prevent the British gaining supplies) and later British depredations (and blockade) caused great disruption. The lower Delaware Valley came out of the war a little better than other areas, but the economy was in tatters at the end of the Revolution.
In the 1780s the war between France and Britain caused great opportunities for the grain trade of the Mid-Atlantic states, but risks also. Seizures at sea of grain by the French navy led to a brief and undeclared naval war between the United States and France in the next decade, problems with Britain contributed to the war of 1812 later. In 1789 the grain trade in the Mid-Atlantic states had recovered from the Revolution and was not yet too damaged by the troubles in Europe. Things were relatively smooth for the large farmers in the Mid-Atlantic, and the shipping business was doing well in consequence. The large shipping businesses in New York and down the coast from there were prosperous at this time. Smuggling had been brought largely under control by the local governments and the US, something the British had never been able to accomplish in their colonies.
The first link below is to the National Archives and Records Administration, which has a great many records on this subject and much more.
Generally speaking the Mid-Atlantic states in 1789 included New York, Pennsylvannia, New Jersey, New England to the north and went as far south as Delaware, Maryland, and Virginia. However, it was not long before Virginia and to a lesser extent Delaware and Maryland would be characterized differently. Economically speaking the states with ocean borders Massachusetts, New Jersey and especially New York were places of trade, commerce, and business. Maryland had Baltimore an economic treasure whose only fault was its geographical location with regard to 'the south'. The south was dominated by the plantation system. A single cash crop, dependent upon the institution of slavery, self contained, and for the most part isolated from other plantations. Although one country by 1789 these regions had vast differences in their economics, the south had the cotton the north had mill and textile production. The relationship became the 'north' and 'south' and that great divide would ultimately test not only the economics of the United States, but define the United States for the next 76 years. Check out the enotes link, it provides more insight to further answer your question.