Most of Maryland's settlement at this time had been on the lower Potomac and around the lower Chesapeake shores. In 1669, Lord Baltimore declared the establishment of new counties on the Atlantic coast, and tried to encourage settlement in the area by offering lower rates for land ownership

. 'Ordered that from the hore kill to the degree forty Northerly Latitude be erected into a County called by the name of Durham and from the hore kill to Mount Scarborough be like wise erected into a County and Called as the Lord Proprietary shall hereafter direct. Ordered that Notice be given to the Sheriffs of Somerset Dorchester Talbot & Baltimore Counties that what Persons will seat on any Lands on the Seaboard Side and Deleware Bay from the Bounds of Virginia to the degree forty Northerly Latitude shall for their encouragement pay only one Shilling Sterling rent per Annum for every fifty Acres which he or they shall take up...'(AOM 5:56)

'hore kill' also know as Whorekill, was the site near present-day Lewes, Delaware, that Swanendail once stood on. Settlement of Marylanders proceeded slowly, as the coastal towns now under the rule of the Duke of York steadily expanded.

At the same time that he ordered the creation of the new counties, Lord Baltimore sent out an expedition to find his northern boundary.

'Ordered that the Surveyor General do make out the Northerly bounds of this Province as near as Possible at the degree forty Northerly Latitude and return his Observations to the deputy Lieutenants in Council...'(AOM 5:58)

When the expedition arrived at New Castle in November of 1669, they observed the latitude to be below 40 degrees, and sent a lettr to the Duke of York informing him that New Castle belonged to Maryland.

'...found the said New Castle by Observation made this day the six and twentieth day of November 1669 to lye in thirty Nine Degrees thirty minutes Northerly Latitude which is thirty minutes to the Southward from the Northern Bounds of the Land Granted by his Majesty of Great Britain to the Lord Proprietary of Maryland as by his Lordships Patent more largely doth appear but understanding the said Town of Newcastle (since his Majesty was most Graciously pleased to send forces to reduce it from the usurped Power of the dutch) hath been protected under the Government of New York I could no less but acquaint your Honour with the claims I have made...'(AOM 5:58)

It is unknown whether or not this expedition actually arrived at the location of the 40 degree line.

In 1673, during the 3rd Anglo-Dutch War, the Dutch returned to conquor New York, New Castle and the other settlements on the Delaware. The following year, the war ended, and England and the Netherlands returned conquested lands to each other. The settlements on the Delaware were again under English control. These settlements were still ruled as part of New York, and Maryland's claims were kept quiet because the Duke of York's government operated with royal approval.

As it stood, it seemed Maryland would never gain control of these growing settlements on the Delaware, but there were still no official boundaries to indicate where Maryland ended and the Duke of York's dominion began.