The current state border between New York and Connecticut more or less follows the effective border between New Netherland and Connecticut before 1655, except that eastern Long Island was under English control. The Dutch claimed up to the Connecticut River valley, and a few Dutch settled there, but were unable to defend the region and English settlers filled the area in, forming the colonies of Hartford and New Haven on Dutch-claimed territory. During the English Civil War and the era of the Protectorate (1643-1660), the colonies of Massachusetts, Plymouth, Providence Plantations, Hartford and New Haven formed an alliance, the New England Confederation, which sent troops to fight the Dutch during the First Anglo-Dutch War in 1655. The alliance was ultimately eliminated during King James II's attempt to form a Dominion of New England in 1686. The governor of the Dominion, Sir Edmond Andros, ruled from New York; I don't think the Confederation that preceded it had a formal capital. A treaty between Governor Stuyvesant and the English confederation formally ceded the Connecticut River valley and the eastern tip of Long Island in 1650, but the Dutch West India Corporation refused to ratify it.From then on until the final cession of New York to the English in 1674, the effective border ran between Westport and Harlem - pretty much the current state border - and across Long Island at about Oyster Bay.