Primary unit numbers
While there is no national standard for how primary unit numbers are organized in the US, our data suggests that cities tend to use a consistent logic. Generally, primary unit numbers on a street consistently increase or decrease in a directional order with even and odd numbers being on the opposite sides.
Primary unit numbers are usually not consecutive. This results in some primary unit numbers being more popular than others. For example, we frequently see multiples of five.
These figures also highlight some of our cultural norms. 13 is perceived to be an unlucky number, and there is a sharp decline for number of addresses that utilize it. There are roughly twice as many addresses that utilize the primary unit 15 over 13.
If we zoom out, we can see that these patterns repeat. A common city planning strategy is to have every block represent a value of 100 primary unit, which makes it easier for individuals to navigate.
Most cities determine a few baselines from where these numbers originate. When using a map that identifies these baselines (by looking at the density of primary unit number 1), we can identify areas of interest in cities.
San Francisco is a city that is set with against several different grids, all of which converge in unique ways. San Francisco’s main thoroughfare, Market Street, is a baseline for the neighboring streets that lie north and south of it. There is a higher concentration along the city of San Francisco’s borders, except for the northern border, where parks are located.