Note: The original letter, sent August 16, 2001, has been modified for the lay reader.
CD-ROMs containing official census redistricting data. The first CD-ROM contained population data, and the second furnished geography information.
As a result of distributing this data, it’s become clear that a technical and crucial clarification between the boundaries of voting districts and official precincts is necessary. The Summary File CD-ROM may provide the false impression that voting districts (also called VTDs) and precinct boundaries are identical. Examining the TIGER/Line® geography is particularly significant: boundaries of voting districts may not match the boundaries of the official precincts, even if the numbers and names of the voting districts exactly match the numbers and names of the official precincts.
In the Census Bureau data provided for Washington, there are more than 7,200 voting districts that are based on official precincts. As a result, the Census 2000 Summary File CD-ROM for Washington state includes tabulations of population totals by major race groups and Hispanic origin, total population, and population of persons 18 years and older for each voting district.
By way of background, Census Bureau data are gathered and reported based on census blocks, the smallest areas of census geography. The boundaries that make up census blocks are determined by a limited number of bureau-approved features, including visible physical features — roads, rivers, mountains — and incorporated place boundaries. The bureau derives data for higher-level geography, such as voting districts, cities and counties by combining all the block data for voting districts, cities or counties.
Conversely, the invisible straight lines — section, range, township, etc. — used frequently by counties as official precinct boundaries were not acceptable to the Census Bureau for delineating voting districts. Given the interest in obtaining census data at the precinct level, the official precinct boundaries had to be approximated using acceptable census features. The resulting areas are the voting districts.
Every effort was made to align voting district boundaries as closely as possible to official precinct boundaries. However, the differences between the state’s legal requirements for official precinct boundaries and Bureau requirements stipulating the use of physical, visible features for voting district boundaries mean that while some voting districts match the official precinct boundaries exactly, many do not. Generally speaking, the voting districts most likely to directly match precinct boundaries are concentrated in urban and/or incorporated areas. (Reviewing the provided TIGER/Line® geography is the most effective way to directly compare official precinct boundaries with Census Bureau voting districts.)
Electronic (.PDF) files of Census 2000 Voting District/State Legislative District Outline Maps, which contain TIGER/Line® geography only, can be downloaded from the Bureau’s Redistricting Data Map Products Web site at: http://www.census.gov/geo/www/tiger/rd_2ktiger/pl_maps/pl_maps.html#tract. Paper copies of the census maps are also available from the Commission upon request.
Any follow-up questions should be directed to the Commission staff at (360) 586-9000.