James Grant, along with other talented surveyors and draftsmen such as Charles Blaskowitz and Thomas Wheeler, was employed by Samuel Holland, Surveyor General for the Northern District of North America on an on-going survey of the North American coastline which was started in 1765. Unfortunately, very little is known about Grant, as with several others of this very talented group who did so much to lay-down what was the most ambitious survey project ever undertaken.

Every one of this team of surveyors and draughtsmen were capable of working on their own or in small collaborative groups. During this period, leading up to the War of Independence, Grant was paired, more often than not, with Thomas Wheeler. Together they produced a series of surveys down the Eastern seaboard from the mouth of the St.Lawrence River, St John's and Nova Scotia down through Maine, New Hampshire and Massachusetts under the direction of Samuel Holland. Several of their surveys were adapted by J.F.W. Des Barres for inclusion in his folios of the Atlantic Neptune. Between 1770 and 1774 the survey team, including Grant, was based in Portsmouth NH. In 1771 he was sent by Holland to survey the source of the Connecticut River and the boundary between New Hampshire and Connecticut, which proved to be the source of much controvesy over the next few years.

His name appears consistently in the Muster Books of HMS Canceaux, British survey vessel attached to the survey, from 1775 at the outset of the Survey, along with Charles Blaskowitz. He is credited as Deputy Surveyor. The last (found) entry for Grant in April 1776 is that of a Surveyor and Draughtsman with a servant - one Charles Mate.

Once the war started little is known of his actions but he  is associated with a Plan of Perth Amboy in 1777 but little else.