Census Data for Mercer Island ...
The most recent Census Estimate<1> was for 2019 and it gave Mercer Island a population of 25,877 people.
The last Decennial Census<2> was in 2010, which gave Mercer Island a population of 22,699 people.
The city of Mercer Island is located in King County. The 2010 Census gave King County; a population of 1,931,249 people. This means that Mercer Island had 1.18% of the county's total population, making it King's 16th most populous community.
At the same time, Washington had a population of 6,724,540 people, meaning that Mercer Island had 0.34% of the total population of Washington - making it the state's 42nd most populous community.
The 2010 Census shows that the sampling area for Mercer Island has a total area of 13.11 square miles [34 km²]. Of this total, 6.32 square miles [16.4 km²] is land, with the balance (51.8%) being water (6.79 square miles [17.6 km²]).
King County has a land area of 2,115 square miles [5,479.3 km²]. At 6.32 square miles [16.4 km²], Mercer Island has 0.3% of the county's total land area.
- Continue Reading ...
- When the Census Bureau conducts a census for a city like Mercer Island, they draw a boundary around the area in which they are going to conduct their count - this defines the sampling area (usually a polygon). The shape of the sampling area can be quite complex and it's important to keep in mind that the boundaries of the sampling area may or may not match the recognized boundaries of the city.
- Things like population, area and housing for Mercer Island reflect the sampling area. Since the shape of the sampling area and the actual boundaries of Mercer Island might be different, it's best to check with the U.S. Census Bureau to resolve any difference between the two.
- Not only does the sampling area define boundaries, it also has a GPS location (latitude & longitude) that indicates a point within the sampling area (usually the center of the polygon, known as the centroid). At the time of the 2010 Census, the sampling area was located at:
- Lat: 47° 34' 3" (or 47.57°)
- Lon: -122° 13' 57" (or -122.23°)
- More information on this topic and the changes between the 2000 Census and the 2010 Census can be found in the section for our Census-to-Census Observations ... (see below).
Housing Units ...
At the time of the 2010 Census, Mercer Island had 9,930 Housing Units<3> and with its population of 22,699 people, this averages 2.29 people per Housing Unit.
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- The 2010 Census shows Mercer Island had a land area of 6.32 square miles [16.4 km²]. This translates to 757 Housing Units per square mile [292.4 housing units/km²].
- From the Census of 2000: Mercer Island had 8,806 Housing Units, a population of 22,036 people and a land area of 6.38 square miles [16.5 km²]. This gives a density of 2.5 people per Housing Unit and 671 Housing Units per square mile [259.4 housing units/km²].
- Note: Repeating the caution above (under Population Density), be aware that when comparing Housing Units between the 2010 and the 2000 Census, there were changes in the sampling area for Mercer Island and you need to be careful when comparing values between the censuses. More information about these differences can be found in the section called Census-to-Census Observations ... (see below).
King County ...
The community of Mercer Island is located in King County<4>.
The county had a population of 1,931,249 people at the 2010 Census. With it's population of 22,699 people, Mercer Island represented 1.18% of the county's total.
In addition, where the city of Mercer Island has a population density of 1,731 people per square mile [668 people/km²], King County averages 912 people per square mile [352.5 people/km²].
For more information, please visit our Census Page for King County.
Census-to-Census Observations ...
When the Census Bureau takes a census count (or enumeration) for Mercer Island, they start by specifying the boundaries of the area to be counted. This area (or sampling area) is a polygon and its shape can be quite complex - it may or may not match the geographical boundaries of Mercer Island. It's important to note that from one Census to the next, the shape and location of the polygon can change.
- Continue Reading ...
- Although we don't have specific information about the shape of the polygon for Mercer Island or how it changed has over time, there is some information that can give us some hints. For example, since the shape of the sampling area is directly related to the shape of the polygon, any change to area probably indicates a new shape for the polygon.
- If you need precision or details about the methodology of the Census, you should visit the U.S. Census Bureau for a definitive answer.
While generally coinciding with the GPS location (latitude/longitude) of Mercer Island, the latitude and longitude given by the Census Bureau actually indicates the GPS location of the polygon for Mercer Island.
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- For the 2010 Census, the location was given as:
- Lat: 47.567716° (or 47°34'3" N)
- Lon: -122.232776° (or -122°13'57" W)
- For the 2000 Census, the location given was:
- Lat: 47.569271° (or 47°34'9" N)
- Lon: -122.232337° (or -122°13'56" W)
- The difference indicates that the U.S. Census Bureau moved the location of the polygon for the 2010 Census 577 feet to the south<5> of the location that was used in the 2000 Census.
- The U.S. Geological Survey (USGS) and the U.S. Board on Geographic Names (BGN) have assigned a unique GNIS identifier (#2411082) to Mercer Island. This identifier also marks a GPS point on the map, and that point lies within the boundaries of Mercer Island. The GNIS point has been mapped to the latitude/longitude:
- Lat: 47.567758° (or 47°34'3" N)
- Lon: -122.232500° (or -122°13'57" W)
- The GPS location given for the 2010 Census lies 69.6 feet to the west<6> of the point given by the GNIS for Mercer Island. For more information about this and the relationship of the various Federal Codes, please visit our Misc Page for Mercer Island.
Miscellaneous Information for Mercer Island ...
The Federal government has assigned various identifying codes to each community, county and state. At one time or another, the US Census Bureau has used one (or more) of the following identifiers when referring to either King County or the city of Mercer Island:
- The GNIS Codes ...
- The current system of identification is called the Geographic Names Information System (GNIS). The following GNIS codes relate to Mercer Island:
- GNIS ID for Mercer Island: 2411082
- GNIS ID for King County: 1531933
- GNIS ID for State of Washington: 1779804
- Misc. Census Codes ...
- Mercer Island is located in Census Region #4 (the West Region) and Division #9 (the Pacific Division).
For more information about the various Federal identification codes, please visit our Misc Page for Mercer Island.
Other Roadside Stops ...
Search for a Washington Community
About King County
Off-the-Road Links ...
The official website for Mercer Island: www.ci.mercer-island.wa.us/
The official website for King County: www.metrokc.gov/
The official website for State of Washington: https://access.wa.gov/
The official website of the U.S. Census Bureau
The official website of the U.S. Board on Geographic Names (BGN)
The official website of the U.S. Geological Survey (USGS)
|<1>||Every year, the US Census Bureau creates a population estimate for the preceeding year. Keep in mind that this value is an estimate and not an actual count. The most recent Census estimate is for the year 2019.|
|<2>||Every 10 years (eg- 1990, 2000, 2010), the US Census Bureau conducts a Constitutionally-mandated count (or enumeration) of people living within the United States. This count is called a Decennial Census. The last Decennial Census was the 2010 Census, with the next one planned for 2020.|
|<3>||A Housing Unit is a broad term for those places where people live (whether occupied or temporarily vacant), such as a house, an apartment, a mobile home, or an area that is considered as a separate living quarter. Separate living quarters (consisting of one or more rooms) are considered to be those places where people live, sleep and eat separately from others and that have access to the outside (either directly or by a shared hallway).|
|<4>||If you're interested in how the shape of Washington's counties, including King, have changed over time, we recommend the Atlas of Historical County Boundaries.|
|<5>||The calculated bearing (or angle) to the 2010 Census location is 169 degrees and a distance of 577 feet.|
|<6>||The calculated bearing (or angle) to the GNIS point is 102 degrees and a distance of 69.6 feet.|