In the United States, address numbers are assigned based on their proportional distance from an assigned baseline. This often creates a big gap between numbers. To further aid location, odd and even numbers are separated to one side of the street or the other.
Many addresses jump by 100 at cross streets, sometimes within each block. For example, a block numbered 2103, 2109, etc. begins as 2203 on the next block. Until the 911 became commonplace, an old rural address could be Route 3, Box 11. However, 911 forced naming streets and numbering houses, generally with a numbers increasing by 1000 for each mile from the nearest town center.
County layout determines some addresses. A baseline is put in one corner of the county, and numbers increase from that point. For instance, an address on a north-south road 17 blocks north from the baseline is written "N1700." An address 54 blocks west of the baseline on an east-west road is displayed as "W5400." Many cities combine baselines so an address might read as "N1700-W5400."
Hyphens sometimes separate the hundreds from the tens digit. For "111-22," the first number generally refers to the street where numbering begins. So for "11-23 21st Avenue," 11 indicates numbering that begins on 11th Street.
For a compound block number system, "53 N 1800 W" shows the number of blocks from the intersection of north-south and east-west roads. More conventional systems might read this as "53 18th Ave NW."