The Reason Utah Addresses Look Like Math Problems to Everyone Else
An address made of two big numbers and a compass letter or two can stop a newcomer in their tracks.
Utahns, especially around Salt Lake City, use a grid system that’s more logical than it looks.
Here’s where it came from and how to make sense of it.
Zero Point at Temple Square
Salt Lake County’s address grid starts at one downtown intersection, South Temple and Main Street in Salt Lake City.
The county’s ordinance calls those two streets the baseline and the meridian of its countywide grid.
If you stand on that corner, you’re at zero on both axes, and one block east of there you’re at 100 East.
Surveying began from an initial point at the southeast corner of Temple Square, according to the Utah County Surveyor.
The spot dates to August 3, 1847, when surveyor Orson Pratt fixed it.
The zero point came well before the finished temple.
Construction began in 1853, and the capstone didn’t go on until 1892.
The city’s streets were numbered outward from that site.
Chain Behind the Math
A 66-foot surveying tool called the Gunter chain is the unit behind each Salt Lake City block.
Ten chains make 660 feet, the length of one Salt Lake City block, and each block gets 100 numbers.
If you walk from 100 East to 200 East, you’ve covered 660 feet.
A statute mile was 80 chains, according to the state’s mapping office.
Eight blocks of ten chains fill that mile, which makes 800 address numbers.
An acre equals ten square chains, which kept land arithmetic tidy.
How Far Is 2100 South?
Salt Lake City’s grid lets you turn an address number into miles by dividing it by 800.
Take 2100 South: 2,100 divided by 800 comes to about 2.6 miles south of South Temple.
The math works on east and west streets, too, so 1300 East sits about 1.6 miles east of Main Street.
These are straight-line figures on paper, so you can sanity-check a route, but expect a few turns along the way.
Big Blocks From the Plat of Zion
The grid traces to the Plat of Zion, a city plan Joseph Smith designed in 1833.
Brigham Young adapted that plan for Salt Lake City in 1847, with blocks 660 feet square and streets 132 feet wide.
Salt Lake City’s large intersections are based on two chain lengths, or 132 feet.
Young cut the lots on each block from 20 to eight, and each lot ran 1.25 acres.
Streets get their numbers from their distance from that central point.
Psst! How much do you know about Utah street addresses? Flip each card and see how many you can get right.
Survey Under the Streets
The state’s mapping office says Salt Lake City uses a section-based addressing system that comes from the federal Public Land Survey System.
It describes each 100-number block, such as 100 East to 200 East, as ten chains, or 660 feet, which it calls a quarter-quarter-quarter section.
According to the Utah County Surveyor, descriptions based on that survey system are still commonly used for legal land descriptions today.
House Numbers as Distances
House numbers on the grid don’t count houses.
They measure distance.
Salt Lake County’s ordinance defines a frontage number as a number assigned by a property’s relative distance perpendicular to the baseline or meridian axis streets.
A frontage scale is 400 numbers per 2,640 feet, which is half a mile.
Outside Salt Lake City, street numbers are measured to the centerline of the roadway.
In 250 West 500 South, 250 West puts the house west of Main Street.
500 South names the street five blocks south of South Temple.
If you swap West for East, you land on the same street on the other side of Main Street.
500 South sits 500 numbers from South Temple, about five-eighths of a mile on paper.
Read together, the two numbers work like a coordinate pair, one counting from each axis.
A Different Zero in Each Town
Not every address grid starts at Temple Square.
The Utah Geospatial Resource Center says each municipality or county may set an origin point.
Logan counts north and south from Center Street, while St. George counts from Tabernacle Street.
Their zeros sit at different crossings, so the same street number means a different spot in each town.
If you’re driving between towns, you’ll want to know whose zero you’re counting from.
Corner Lots and Spreading Grids
Salt Lake County’s address standards cover corner lots, where one building touches two streets.
A subdivision’s corner lots should get frontage numbers calculated for both streets.
Both numbers go on the final plat.
If you live on a corner in Salt Lake County, your address comes from the street your building faces.
In Salt Lake County, rural areas with older numbering systems must convert to the countywide grid once they incorporate, are annexed, or become part of the county’s urban growth.
The state’s mapping office says you could argue Latter-day Saint pioneers helped carry the Plat of Zion pattern west by establishing more than 700 communities.
Four-Quadrant Trap
Four quadrants explain why you can’t leave the compass letter off an address.
The state’s address data splits each grid into northeast, southeast, southwest and northwest quadrants.
Numbers repeat across them, so 400 South and 400 North are different streets on opposite sides of South Temple.
They aren’t close.
Eight hundred numbers separate them, about a mile on paper.
Salt Lake County’s standards abbreviate each direction to one letter: E, W, N or S.
That letter tells you which way to count from the junction of the baseline and meridian streets.
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