I've noticed that in the US, states created before the Civil War had north-south borders defined by geographic features, and afterwards, had borders defined by what appear to be latitude.
I know from the history of longitude, that knowing one's east-west location generally requires measuring the time the sun is at it's zenith. And I've heard while visiting the Museum of Industry that the Waltham Watch company had a large effect on the availability of timekeeping devices starting in 1850, and really kicking off in 1860.
Is there modern scholarship or contemporary reports on the effect of readily available pocket watches allowing US surveyors to accurately define north-south lines, or lawmakers taking this into account as new state borders were being drawn?
Finding longitude and latitude were very big problems for a ship out on the ocean. It was impossible to precisely measure the distance from one day to the next with no hard and fast landmarks, and the actions of currents and imprecise speed gauges made it hard to correlate knots with actual travel. Use of navigational tools like sextants and chronometers were key. However, for surveying on land, that was not the case. From a precisely measured base line, triangles could be laid off to map any piece of ground. The typical tools of chain, plumb bob, and transit would suffice. Sightings of the sun would not be needed, or precise time measurement. They would of course be needed to place continents and islands in the correct distance from each other.
