National Pre-Redistricting (2021 Cycle) State Legislative District Boundaries and Block Assignment File

## RDH Creation Date
03/08/2023

## Sources
This file is intended to represent the last state legislative boundaries drawn using 2010 census data in each state at both the lower house and upper house levels. As such, this data represent the state legislative districts in effect prior to the 2021 redistricting cycle. In some cases, states have not yet passed new legislative maps or conducted elections on new maps post redistricting, and these maps may still be in effect.

The primary source for the data in this file is the 2020 census P.L. data, specifically the "SLDU18" and "SLDL18" fields. In instances where state legislative maps have been redrawn since 2018 but prior to the 2021 redistricting cycle, state legislative district information was swapped with official maps from All About Redistricting via the Redistricting Data Hub website. Block assignment files were created using the maup software package.

Updates occurred in between 2018 and 2021 for: VA SLDL, TX SLDL, NC SLDL, MS SLDU, and NC SLDU. Data for these states and levels was swapped in using files from the RDH website.

Please note that NH is the only state with both base and floterial districts. The floterial districts are stored in a separate file to prevent unintentional overlaps in processing. The SLDL block assignment in the census data is used to create the base districts, and the floterial districts were created using these base districts.

## Fields
Field Name Description
***national_pre_2021_redistricting_st_leg_boundaries_baf.csv***
GEOID20    2020 Census Block GEOID
SLDU       State Legislative Upper House District Name or Number
SLDL       State Legislative Lower House District Name or Number
FLOTERIAL  Floterial District Name or Number

***national_pre_2021_redistricting_st_leg_lower_nh_floterial_boundaries***
DISTRICT   District Name or Number
STATE      State Abbreviation

***national_pre_2021_redistricting_st_leg_lower_boundaries***
DISTRICT   District Name or Number
STATE      State Abbreviation

***national_pre_2021_redistricting_st_leg_upper_boundaries***
DISTRICT   District Name or Number
STATE      State Abbreviation

## Processing Notes
2020 block-level census data and census block shapefiles were retrieved from the Redistricting Data Hub website.

In the instances where state legislative maps had changed since 2018, block assignments were swapped after creating block assignment files using the maup software package.

Please note that these plans were originally drawn on 2010 blocks, and as such there may be multiple defensible methods of representing these plans on 2020 blocks. This is true of the census' assignments as well.

Names and numbers of various districts were cleaned and standardized in part to create the NH floterial districts.

Census block assignments were joined to the census block boundaries and dissolved to form a state legislative lower house district file, state legislative upper house district file, and a state legislative lower house floterial district file.

## Additional Notes
In the BAF, the "FLOTERIAL" field is not applicable and marked "NO FLOTERIAL" for all states except New Hampshire. In New Hampshire, the state legislative lower house has both base districts (represented by the 'SLDL' field) and floterials (represented by the "FLOTERIAL" field). Not all blocks in New Hampshire are nested within a floterial and those that are not are assigned "NO VALUE" in the "FLOTERIAL" field.

For states with one map for state legislative districts, the same values were used for the "SLDL" and "SLDU" fields. Nebraska is an exception to this, as it does not have a lower chamber in its state legislature, so for the "SLDL" field all blocks are assigned "NO SLDL". Some blocks may not have assignments for SLDU or SLDL districts. These blocks are given "NO VALUE" in their respective fields.

When creating the district shapefiles, "NO VALUE" and "NO SLDL" districts are filtered out.

Please email info@redistrictingdatahub.org for any questions about this dataset.