Located south of Centralia, Illinois.

The historical marker, called the Cardinal Point Witness Corner, was erected in June 1976 to mark the intersection of the Third Principal Meridian and the Illinois Base Line. The marker includes the offset to the original Point of Beginning marker, which is now under the surface of Highway 51. The marker also to serves as an officially surveyed offset point (known as a witness corner), since the original location was beneath the highway - until it was recently dug up and made more accessible with the installation of a manhole cover.

3rd Principal Meridian Cache

Another 100th Meridian Marker

Benchmark on Buttermilk Hill

Geodetic Center-as close as you get..

Dating back to 1840, this last known of the markers for the borderline of the Republic of Texas.  Located 10 miles southeast of Deadwood, Texas on Farm-to-Market Road 31. Its role is unofficial now, except to let you know when you’ve left Louisiana and give you a little history of the old republic and the disputed border along the Sabine River. There were many of these stone markers at the time, but this one, which is on the National Register of Historic Places, is the only one that hasn’t either disappeared or sunk into the river.

The granite pillar is 9 inches square and sticks up about 4 feet from the ground. An accompanying plaque notes that it’s actually 10 feet long, which means it’s buried several more feet—a feature that has kept it from being stolen, at least on one reported occasion. Three sides are engraved, providing all the necessary details: Merid. Boundary, Established A.D., 1840 (the marker is dated 1840 but was actually planted in 1841) on one side, and sides two an

Last remaining boundry marker TX - Clueless&Clumsy

Louisiana Purchase State Park, in eastern Arkansas.

Located at the Initial Point from which all surveys of the property acquired through the Louisiana Purchase of 1803 initiated.

https://en.wikipedia.org/wiki/Louisiana_Purchase_State_Park

Louisiana Purchase ParkCache

Commemorative marker located on Eight Mile road in Novi, Michigan. 

Marks the 1815 survey to lay out the East-West Michigan baseline, the basis for the layout of the all of the farms and other lands in Michigan.

The obelisk erected here is one of several which make up a series called “Coasting the Baseline.” All markers in the series share a discussion of the basic surveying tools, the measurement chain and staff compass. 

Michigan Base Line Monument

At this site is an iron marker for the northwest corner of the Territory of Missouri. It was placed in 1850, to identify the territory boundary as determined by the 1816 Sullivan survey. When Missouri became a state, the border moved west to the Missouri river at the same latitude. The location is now a boundary road between Missouri and Iowa.

A engraved stone monument was recently been placed next to the iron marked by the Virginia Daughters Chapter of the NSDAR.

N.W. Corner of Missouri 1850

Near Eitzen, Iowa

At the Initial Point, the first marker of the 1852 survey to establish the boundary between the Iowa and Minnesota territories at the parallel of latitude of 43° 30' north.

http://iagenweb.org/allamakee/history4/ironpost.htm

Oak Post Historical 

On the Kansas-Nebraska border near the Missouri River.

Virtual cache located at the Point of Beginning of the public land survey establishing the 6th Principal Meridian.

Point of Beginning

RI - CT- MA Tri-state Marker

Nice write-up at http://www.pmproject.org/2pm.htm

Second Principal Meridian

South Central Meridian point

At the Initial Point of the Cimarron Meridian, which established the border between Oklahoma and New Mexico. The baseline established by this initial point was intended to define the east/west boundary between Texas and what would become Oklahoma, however, due to surveying errors, the official state line runs parallel to it, a few hundred feet south.

The Cimarron Meridian was the last meridian established as part of the federal land survey in the Lower 48 states. It was created in 1881, in order to survey a federal no-man’s land between Kansas, Colorado, New Mexico, Texas, and Oklahoma, an artifact left when Texas reduced its northern extent by half a degree, to fall below the 36 degree 30 minutes line of latitude, which would allow it to be a slave state, at the time Texas joined the Union in 1846. Once surveyed, this region became part of the Oklahoma Territory.

http://www.clui.org/section/cimarron-meridian

Texhomex

On the border between Kansas and Nebraska.

A red sandstone marker lies under a manhole cover in the middle of Meridian Road.  This is the Initial Point of the Sixth Principal Meridian. The point, established for the 1855-56 westward survey, controls the system of sections, townships and ranges of the public land surveys in Nebraska, Kansas and parts of Colorado, Wyoming and South Dakota. This Initial Point is referenced in all ownership records throughout the system.

On June 11, 1987 the Professional Surveyors of the 6th Principal Meridian dedicated a memorial to the spot.

The 6th Principal Meridian

At the Beginning Point of the U.S. Public Land Survey which was initiated in 1785. The plaque at the site states that the true starting point was 1,112 feet further south of this location, which is at the three-way intersection of Ohio, Pennsylvania, and the northern tip of West Virginia.

https://en.wikipedia.org/wiki/Beginning_Point_of_the_U.S._Public_Land_Survey

The Alone Ranger

The Point of Beginning

The Survey Meridian

THREE 100th Meridian Markers

Tri-State Cache

This is a list of Geocaches across the US located at or otherwise commemorating historically significant points along base lines, meridians, or other survey markers.

https://en.wikipedia.org/wiki/Baseline_%28surveying%29

Anyone is welcome to add caches to this list as long as they meet the criteria.

Historical US Survey Caches.list-details-1wr9x6v{text-transform:uppercase;font-size:12px;}@media screen and (min-width: 600px){.list-details-1wr9x6v{font-size:1.25rem;}}.list-details-1wr9x6v.shareable{color:#87705a;}.list-details-1wr9x6v.public{color:#00b265;}Public

Historical US Survey CachesPublic