Editing Mason–Dixon line (section)

==Geography of the line==
[[File:Delaware-wedge.svg|thumb|Diagram of the survey lines creating the Mason–Dixon line and [[Wedge (border)|The Wedge]]]]
[[File:Marycolony.png|thumb|The [[Province of Maryland]], 1632–1776]]
Mason and Dixon's actual survey line began to the south of [[Philadelphia]], and extended from a [[Benchmark (surveying)|benchmark]] east to the [[Delaware River]] and west to what was then the boundary with western Virginia.

The surveyors also fixed the boundary between [[Delaware]] and [[Pennsylvania]] and the approximately north–south portion of the boundary between Delaware and [[Maryland]]. Most of the Delaware–Pennsylvania boundary is an [[Twelve-Mile Circle|arc]], and the Delaware–Maryland boundary does not run truly north–south because it was intended to bisect the [[Delmarva Peninsula]] rather than follow a meridian.<ref>{{cite book |title=Drawing the Line How Mason and Dixon Surveyed the Most Famous Border in America |publisher=John Wiley |author=Danson, Edwin |year=2001 |pages=54}}</ref>

Mason and Dixon also confirmed the earlier survey delineating Delaware's southern boundary from the Atlantic Ocean to the "Middle Point" stone (along what is today known as the ''Transpeninsular Line''). They proceeded nearly due north from this to the Pennsylvania border.{{citation needed|date=October 2020}}

The Maryland–Pennsylvania boundary is an east–west line with an approximate mean [[latitude]] of 39°43′20″&nbsp;N ([[datum (geodesy)|Datum]] [[WGS&nbsp;84]]). In reality, the east-west Mason–Dixon line is not a true straight line in the geometric sense, but is instead a [[polygonal chain]], a series of many adjoining line segments, following a path between latitude 39°43′15″&nbsp;N and 39°43′23″&nbsp;N.

The surveyors also extended the boundary line {{convert|40 |miles}} west of Maryland's western boundary, into territory that was still in dispute between Pennsylvania and Virginia, though this was contrary to their original charter.<ref name=hubbard/> Mason and Dixon's survey was finished on October&nbsp;19, 1767, about {{convert|31 |miles}} east of what is now Pennsylvania's southwest corner. Where the surveyors finished their survey became known as the [[Mason and Dixon Survey Terminal Point]]<ref name="Wilford2001">{{cite book |last= Wilford |first= John Noble |title=The Mapmakers: Revised Edition |url= https://books.google.com/books?id=vHy44e1nRXcC&pg=PA215 |access-date= 2012-11-01 |year=2001 |publisher= Random House Digital, Inc. |isbn=978-0375708503 |pages=215–216}}</ref>

In 1774, commissioners from Pennsylvania and Virginia met to negotiate their boundary, which at the time involved Pennsylvania's southern border west of Maryland and its entire western border. Both sides agreed that Pennsylvania's grant made its western border a tracing of the course of the Delaware River, displaced five degrees (approximately 265 miles) to the west. And both sides thought this would place [[Fort Pitt (Pennsylvania)|Fort Pitt]] in Virginia territory (in fact it would not have). With that in mind, the governor of Pennsylvania argued that, despite the agreement reached with Maryland, Pennsylvania's southern border west of Maryland was still the [[39th parallel north|39th parallel]], about {{convert|50 |miles}} south of the Mason–Dixon line. Negotiations continued for five years, with a series of proposed lines. In the end, a compromise was reached: the Mason–Dixon line would be extended west to a point five degrees west of the Delaware River. To compensate Pennsylvania for the claimed territory lost, its western boundary would be run due north rather than copying the course of the Delaware River.<ref name=hubbard/>

The Mason–Dixon line was [[Milestone|marked by stones every mile]] {{convert|1|miles}} and "crownstones" every {{convert|5|miles}}, using stone shipped from England. The Maryland side says "(M)" and the Delaware and Pennsylvania sides say "(P)".<ref>{{Cite web |last=Ecenbarger |first=William |date=2021-06-24 |title=Stolen, vandalized, buried, lost: Mason-Dixon Line markers are getting surveyed to be saved |url=https://www.inquirer.com/news/mason-dixon-line-pennsylvania-philadelphia-maryland-survey-historic-register-20210624.html |url-status=live |archive-url=https://web.archive.org/web/20210624224749/https://www.inquirer.com/news/mason-dixon-line-pennsylvania-philadelphia-maryland-survey-historic-register-20210624.html |archive-date=2021-06-24 |access-date=2022-02-15 |website=[[The Philadelphia Inquirer]] |language=en}}</ref>
Crownstones included both coats of arms.

Many of the original stones are still visible, resting on public land and protected by iron cages; a number have gone missing or were buried.<ref name = "WaPo">{{cite news|first=William|last=Ecenbarger|title=Neglecting the Mason–Dixon boundary stones|newspaper=The Washington Post|date=January 1, 2017|page=C4}}</ref>

The actual locations of the stones may differ a few hundred feet east or west from the exact positions where Mason and Dixon intended to place them, still, the line drawn from stone to stone forms the legal boundary.{{citation needed |date=October 2020}}

The lines have been resurveyed several times over the centuries without substantive changes to Mason's and Dixon's work, and additional [[Benchmark (surveying)|benchmarks]] and [[survey marker]]s were placed where necessary.