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Number One City Datum - Chicago, IL
Posted by: Groundspeak Premium Member adgorn
N 41° 52.842 W 087° 37.938
16T E 447536 N 4636723
Quick Description: Marker for the primary datum for the City of Chicago, the point from which all the heights in the City of Chicago are measured. Located at the NW corner of La Salle & Monroe on the Northern Trust bank headquarters, 50 S La Salle.
Location: Illinois, United States
Date Posted: 4/22/2008 3:42:07 PM
Waymark Code: WM3MZY
Published By: Groundspeak Regular Member GEO*Trailblazer 1
Views: 112

Long Description:
The city datum is...a plane 17.640 feet below the bench mark cut on top of the bottom stone of granite base... Sept 12, 1928.

In 1905, construction began on the new Northern Trust building, built of granite, marble and other materials that would last. Strong concrete pillars reached down to bedrock, 105 feet below street level, to carry the heavy structure above. Years later, city engineers, saying that they considered the building sag-proof, cut into Northern's cornerstone a bench mark known as the Number One City Datum Mark, From this mark the heights of all future structures in Chicago would be measured.

50 South LaSalle was also hailed as the first totally air conditioned building in the City in 1929.
Monumentation Type: other (not included below)

Monumentation Type (if other): wall mounted plaque

Monument Category: other (not included below)

Monument Category (if other): datum

Accessible to general public: yes

Monument Website: [Web Link]

County: Cook County, IL

Approximate date of monument: 09/12/1928

Explain Non-Public access: Not listed

Historical significance: Not listed

USGS Quad: Not listed

NGS PID: Not listed

Other Coordinates: Not Listed

Other Coordinates details: Not listed

Visit Instructions:
1. A closeup photo of the monument is required.
______
2. A 'distant' photo including the monument in the view is highly recommended. Include the compass direction you faced when you took the picture.
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