1980 Block Boundaries

NHGIS 1980 census block shapefiles depict 1980 block boundaries for selected areas throughout the U.S. The current version (v4.0) includes all or part of 148 metropolitan areas. We will update and extend the shapefiles in future releases as we complete more areas.

These files provide a more accurate and complete representation of 1980 block boundaries than is available from the U.S. Census Bureau's 1992 TIGER/Line Files, the only previously existing source of digital 1980 block definitions for the nation.

We currently provide the boundary files through this web page along with documentation and census summary statistics for 1980 blocks. In the future, we will provide both the boundary files and summary tables through the NHGIS Data Finder, where we already provide block summary data for 1970 and both summary and boundary data for all census years after 1980.

• Overview
• Technical Details
  • Basics
  • Geographic Coverage
  • Data for Whole Collection Blocks, Not Tabulation Blocks
  • Popular Tables
• Download: Boundaries
• Download: Statistics
• Feedback and Questions
• Citation and Use
• Credits

Overview

The U.S. Census Bureau's 1992 TIGER/Line Files include both 1990 and 1980 census block boundaries, but the 1980 blocks are badly incomplete and often inaccurate. Of the 2.5 million blocks that appear in the 1980 census summary tables, about 765,000 do not appear in the 1992 TIGER/Line Files, and there are missing cases in nearly every county where block data were provided.

Using the 1980 paper census block maps as a guide, NHGIS staff are manually editing data from the 1992 TIGER/Line Files to recover as many missing blocks as possible. The Census Bureau published the paper maps separately by Standard Metropolitan Statistical Area (SMSA), so NHGIS editing work is also organized by SMSA.

Initial versions of our 1980 block shapefiles will cover only the SMSAs that we have completed. We plan to release more versions including more SMSAs at regular intervals until the project has ended.

NHGIS validates the edited geographic block data against the statistical block data from 1980 Summary Tape File 1 (STF1). For a small portion of the blocks that appear in STF1, we are unable to find corresponding blocks on the paper maps or in the TIGER/Line data, so we cannot provide complete block definitions for all reported statistics. Our validation process produces summaries of the discrepancies between the edited boundary data and statistical data. We supply these summaries for user reference along with the shapefiles.

We also provide separate files of block-level summary tables derived from the 1980 STF1 dataset. This is important because the original STF1 includes data only for block parts and not for the whole collection blocks that the boundary files depict.

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Technical Details

Basics

• The boundary data are stored in shapefiles within ZIP archives
• There is a separate shapefile for each state (or state equivalent) where boundaries are currently available
• There is a nationwide shapefile that includes all block boundaries available at this time
• Two supplemental CSV (comma-separated-values) files accompany each shapefile within the ZIP archives
  • data_missing_polygon - Lists blocks that have records in the statistical tables but do not have polygons in the shapefile
  • polygon_missing_data - Lists blocks that have polygons in the shapefile but do not have records in the statistical tables
• The statistical and boundary files include standard NHGIS GISJOIN identifiers
• The statistical table data are stored in a CSV file within a ZIP archive
• There are two nationwide CSV files
  • One includes all tables
  • One includes a collection of popular tables
• There is a CSV file for each state (or state equivalent) with boundaries currently available
• All ZIP archives include human-readable codebooks describing the contents of the data files

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Geographic Coverage

We plan to produce 1980 block shapefiles for all of the Standard Metropolitan Statistical Area (SMSAs) that are covered (imperfectly) in the 1992 TIGER/Line Files. In 1980, the Census Bureau's block data program covered only urbanized areas and large incorporated places (those with 10,000 or more residents based on pre-1980 sources). State and local agencies also contracted with the Bureau to obtain block data for many additional areas, but the 1992 TIGER/Line Files provide very limited information for the blocks in these areas, so we do not expect to complete those.

The 1980 block shapefiles are organized by state for consistency with NHGIS block boundary files for later years. A given state's shapefile includes blocks only for counties that NHGIS has completed within that state. To obtain all block boundaries for an SMSA that crosses state boundaries, a user will need to combine block files from each corresponding state.

Future versions of the shapefiles will extend coverage within currently included states and add new files for other states. Our work was initially limited to a small set of SMSAs for which we could obtain block maps. We later found lending sources for nearly all SMSAs and have since then prioritized the largest SMSAs.

Some SMSAs do not have complete coverage in our shapefiles. In some SMSAs (e.g. Detroit), our block boundaries cover the central city, but we have not yet completed one or more suburban counties that have no blocks in the 1992 TIGER/Line files.

We detail current coverage by state and by SMSA in this spreadsheet:

• 1980 Block Shapefile Coverage (Excel spreadsheet)

Click below for a list of currently covered SMSAs ordered by population:

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Data for Whole Collection Blocks, Not Tabulation Blocks

The Census Bureau defines two types of census blocks: collection blocks and tabulation blocks. As implied by these names, the Census Bureau generally tabulates and publishes data only for tabulation blocks, not collection blocks. The collection blocks are defined first, before census operations, and their boundaries mainly follow observable physical features like roads, railroads, streams, shorelines, etc. Most tabulation blocks match collection blocks, but tabulation blocks can include additional subdivisions wherever collection blocks are split by higher-level reporting areas, such as incorporated places and minor civil divisions (MCDs). As explained in the Census Bureau's Geographic Areas Reference Manual (p. 11-14), "This methodology permits the Census Bureau to accommodate changes to the boundaries of legally recognized entities as they occur and still maintain a stable inventory of collection blocks."

In 1980 block data and on 1980 block maps, the block identifiers correspond only to collection blocks and do not distinguish the parts of collection blocks (i.e., the tabulation blocks) that lie in different places or MCDs. The Census Bureau revised this practice in 1990, adding suffixes to tabulation block codes to distinguish each part of a split collection block. As a result, every census reporting area at every census summary level now corresponds exactly to a set of uniquely identified tabulation blocks, but that is not the case in 1980 data.

Figure 1. Two STF1 block data records have the same tract and block identifiers but unique place identifiers. We generate new data for the whole collection block with a population equal to the sum of the two split parts' populations.

In the original block-level statistical data in 1980 STF1, there are separate records for each part of a split collection block, each with unique statistics, but without a unique tabulation block identifier. A user must examine the place or MCD codes to determine which part of the collection block each record corresponds to. Unfortunately, there are discrepancies between the place and MCD identifiers in the statistical data and the place and MCD boundaries in TIGER/Line Files and on the paper maps, preventing us from exactly matching the block boundary data to the original tabulation blocks.

To resolve these discrepancies, NHGIS provides boundary data for whole 1980 collection blocks only, and we derive new statistical data for the whole blocks.

The statistical data files include all collection blocks identified in 1980 STF1, including areas not yet covered in the NHGIS boundary files. Out of the 2.5 million blocks identified in 1980 STF1, only about 61,000 are split by place or MCD boundaries. Of these blocks, only 35,000 (those that had non-zero counts for two or more of their parts) required data aggregation.

We derived new data for all tables in the NHGIS dataset "1980 Census: STF1 - 100% Data". That dataset currently provides block data at two geographic levels, which separately cover states with strong MCDs and those without:

• MCD States: State--Standard Metropolitan Statistical Area--County--County Subdivision--Place--Census Tract--Block
• Non-MCD States: State--Standard Metropolitan Statistical Area--County--Place--Census Tract--Block

To aggregate the data, we first sum the counts for all records that share the same codes for state--county--census tract--block. Then for tables that report median values rather than counts, where aggregation is necessary, we use the same method that the the Census Bureau used, interpolating median estimates from the associated binned count data. For instance, to interpolate an estimate for median age, we use the aggregated counts of persons age 0-4, 5-9, and so on. We provide complete details on this methodology in the codebooks that accompany the data files.

The aggregated collection block data are therefore provided at the following geographic level for all states:

• State--County--Census Tract--Block

A more detailed explanation of the aggregation process and variable definitions is available in the codebook that accompanies the data file.

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Whole Block Suppression

Data from 1980 STF1 include suppression, whereby certain counts for blocks with few people or households were not published. When aggregating data for block parts to whole blocks, we suppress data for a given variable whenever at least one of the component block parts had suppressed data for that variable.

In our 1980 block summary statistics, suppressed values are indicated with blanks, but not all blank values are due to suppression; median values that could not be calculated are also left blank. You can use the SUPFLG fields to determine whether a value is suppressed or not. For more information about suppression, see the STF1 Technical Documentation.

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Popular Tables

For user convenience, the tables most requested by NHGIS users are available in a separate CSV file. This file contains 16 of the 82 tables in 1980 Summary Tape File 1. A full description of these tables is available in the codebook, which is included with the data file in the download ZIP file. Click below for an overview of the tables.

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Download: Boundaries

The 1980 block boundaries are available as statewide or nationwide shapefiles.

The nationwide file includes boundaries for all covered metro areas, as listed here:

• Nationwide Shapefile

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Download: Statistics

Summary statistics for whole collection blocks, derived from 1980 STF1, are available as statewide or nationwide comma-separated values (CSV) files.

• Nationwide files:
  • All Tables (424 MB) *
  • Popular Tables Only (121 MB, tables listed here)

* If you run into issues unzipping a data file, we recommend using the Unarchiver tool or the command line. See this IPUMS User Forum post for additional information.

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Feedback and Questions

You may direct any comments or questions about these files to nhgis@umn.edu.

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Citation and Use

Use of the NHGIS 1980 Block Boundary Files is subject to the same conditions as for all NHGIS data. See Citation and Use of NHGIS Data.

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Credits

Our production of 1980 Block Boundary Files is supported by funding from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) (R01HD057929).

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