US States Choropleth Map Maker

How the US States Choropleth Map Maker works

US states choropleth map maker: what to paste

Two columns: a state and a number, one per row, separated by commas or tabs. A header row is optional; when present the value column's name becomes the legend title unless you set one. States can be given as full names (California, New York) or two-letter postal codes (CA, NY), in any case. The District of Columbia is included as DC or Washington DC, and Puerto Rico as PR. Matching ignores case and punctuation. Rows that match nothing are listed under Unmatched rows in the stats so you can correct them.

The Albers USA projection

The map uses the Albers USA composite projection, the layout used by the US Census Bureau and most news graphics: the contiguous 48 states in an equal-area conic projection, with Alaska scaled down and Hawaii placed below the south-west. Because the projection is equal-area for the mainland, a state's shaded region is proportional to its real land area, which is why small but populous states like New Jersey and Massachusetts look insignificant on a choropleth; if your data is per person rather than per state, consider a bubble map or a cartogram instead.

Colour scale and classes

Continuous maps the lowest value to the palest tint and the highest to the darkest, with every value in between placed proportionally. Choosing 4 to 7 classes instead splits the range into equal-width bands, each with one colour, which is easier to read against the legend. Single-hue scales (Blues, Greens, Reds, Oranges, Purples) suit data that runs from little to much; Viridis and Yellow to red give more contrast; Red to blue is a diverging scale for values with a natural midpoint, such as margin of victory or change from last year. States without a value are drawn in light grey and marked "no data" in the legend.

Labels

All names, the default, prints every state's postal code at its centre, which is the usual treatment for a US map since readers know the codes. Names with data labels only states that have a value. Values prints the number itself in short form (1.2M, 45k). Labels are white on dark fills and black on pale ones, and the tiny north-eastern states will overlap at small sizes; export at 2x or 3x PNG for a legible print.

Reading the stats

States with data counts matches out of the 51 states and DC. Highest and Lowest name the extremes, and Total and Mean are computed over matched states only. Hover any state for its name and value, or "no data".

Exporting

Download SVG gives a vector file with one path per state and editable labels. Download PNG renders at one, two or three times the preview width. Copy SVG puts the markup on the clipboard.

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