Anatomy of a Cartographic Surrogate: the Portrayal of Complex Electoral Boundaries in the Congressional District Atlas

Abstract

Compiled and published by the Bureau of the Census, the Congressional District Atlas describes the boundaries of the nation’s 435 congressional districts. Since its inception in 1960, the atlas has grown in length from 103 to 1,272 pages. The most noteworthy increase, between the 1987 and 1993 editions, reflects judicial pressure to equalize district population within a state as well as Department of Justice efforts to maximize the number of minority-majority districts. Single-district states like Delaware and Wyoming still consume a single printed page, and because county boundaries are documented elsewhere, a singlepage map is usually adequate for states in which district boundaries do not split counties. By contrast, non-traditional borders winding through multiple counties require numerous large-scale maps efficiently formatted as telescopically nested insets. In the most recent edition, published in two volumes in 1993, Florida and Texas individually account for more pages than the entire first edition, and North Carolina’s 12th district, which the Supreme Court ridiculed in Shaw v. Reno, stretches across 30 separate pages. Because of this parsimonious portrayal of boundaries, the atlas affords a convenient state-level descriptor of geographic complexity: the ratio of map pages to seats in the House of Representatives. Cartographic and statistical analysis of this index reveals a concentration of complex boundaries in the Southeast and other areas in which the Voting Rights Act mandates preclearance by the Justice Department. Not surprisingly, the index is a near-perfect predictor of judicial challenges to race-based redistricting