The Atlantic coast, and the western shore of the Delaware Bay were host to non-Maryland colonization as early as 1631. The Dutch had claimed lands in the Hudson and Delaware river valleys. New Amsterdam was established in 1626 at the mouth of the Hudson River, and several other trading posts were located along the Delaware River and in surrounding areas.

In 1631 Samuel Godyn, under the Dutch West India Company started a settlement with 32 people at the site of present day Lewes, Delaware. (see figure 3) Swanendael, as they named it, would not last long, and was destroyed by indians less than a year after it was founded. The small settlement was a failure, but its short existence would become a technicality which, later, would cost Maryland a large amount of territory.

In March of 1638, New Sweden was established at the site of present day Wilmington. The 25 settlers erected Fort Christina, and their colony grew with the support of the Swedish government. It is said that the Swedish colonists had more initial success than their English counterparts because they were better prepared for the extreme temperatures of the region. 'Travelers noted the greater warmth and comfort of the Swedish log houses, which became the prototype of the American Frontiersman's abode.'

The Dutch considered Fort Christina to be in the territory of New Netherland. Peter Stuyvesant, the governor of New Netherland was forbidden to attack New Sweden, because the Dutch government did not want to upset relations with Sweden. He instead built Fort Casimir at present day New Castle in 1651. (see figure 3) This Fort was not an immediate threat to New Sweden, but it was situated on land that the Swedih had purchased from indians and claimed. In 1654 Johan Rising, the new governor of New Sweden attacked and conquored Fort Casimir. The fort was not well garrisoned, and the Dutch did not lose much in this attack, but they now had an excuse to retaliate against New Sweden.

In September of 1655, Stuyvesant did just that, with a small fleet and hundreds of men sent from New Masterdam. He quickly retook Fort Casimir and moved on to surround and conquor Fort Christina. Governor Rising surrendered, and turned over all of the territory claimed by New Sweden to the Dutch.

Under the control of the Dutch, the town of New Amstel grew up around Fort Casimir, the town of Altena grew where Fort Christina had been, and a new settlement was established where Swanendael had failed. Also at this time in the late 1650s, these Dutch towns began trading with Maryland, from whom they bought tobacco.

Lord Baltimore sent officials to New Amstel in 1659 to inform the Dutch colonists that they were in Maryland territory, but they paid no honor to his claim. Maryland most likely did not further confront the Dutch for fear of starting international incidents, and also because of the secondary market for tobacco sales that the Dutch presented.

The Duke of York, brother of King Charles II, was granted all of the land between the Delaware and Connectucuit rivers in 1664. He sent a force to remove Dutch rule from his territory, which quickly conquored New Amsterdam, and changed its name to New York. His troops then proceeded to the Delaware River where they conquored Altena and New Amstel, which they renamed New Castle. The leaders of the Duke's forces knew that the settlements on the west bank of the Delaware were not in his land grant, but they saw it as their duty to remove the Dutch. They also knew the land belonged to Maryland, but as the flourishing Dutch-Maryland tobacco trade had established, the land was valuable.