Rittenhouse moved to Philadelphia in 1770, where he set up shop on the corner of Seventh and Mulberry (now Arch) streets and later became the city surveyor of Philadelphia. Rittenhouse was contracted as a surveyor for Great Britain in 1763.

His first public service was a boundary survey for William Penn in 1763-64 to settle a dispute with Lord Baltimore.  He laid the twelve-mile radius around Newcastle, Delaware which forms the boundary between Pennsylvania and Delaware.  Rittenhouse’s work was so precise and well documented that it was incorporated without modification into the later survey by Charles Mason and Jeremiah Dixon (England’s most admired surveyors) of the Pennsylvania-Maryland border.  Later Rittenhouse would help establish the boundaries of several other states and commonwealths both before and after Independence, including the boundaries between New Jersey, New York, and Pennsylvania. Mason and Dixon began a survey of the Pennsylvania-Maryland border in 1763 but that survey was interrupted in 1767. In 1784 Rittenhouse and Andrew Ellicott completed this survey of the Mason-Dixon line to the southwest corner of Pennsylvania. Along the way, they set a post on the north bank of the Ohio River.  That marker was adopted later that year by Thomas Hutchins as the Initial Point for the survey of the Seven Ranges and became the starting point for subdividing the public lands of the United States under the Land Ordinance of 1785.

David Rittenhouse made topographic surveys for roads and rivers, and he likely performed property surveys as well.  He was the City Surveyor of Philadelphia for part of 1774.  Several of the instruments made by David Rittenhouse show mechanical ingenuity. He is generally credited as the inventor of the vernier compass which allows more precise bearings to be sighted.  He made and repaired instruments for George Washington.  Benjamin Franklin consulted him on various occasions.  For Thomas Jefferson he standardized the foot by pendulum measurements in a project to establish a decimal system of weights and measures. 

The Revolutionary War interrupted Rittenhouse’s manufacturing, and afterward he engaged in other activities, including state boundary surveying. Nonetheless, in 1780 he sought good optical glass for grinding telescope lenses, and reportedly produced surveying instruments into the 1780’s.

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