The Savannah sparrow was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae.

[5] The specimen has not survived,[6] but a coloured drawing of the bird made during the voyage by the artist and naturalist William Ellis is now held by the Natural History Museum in London.

[7][8] The Savannah sparrow is now the only species placed in the genus Passerculus that was introduced in 1838 by the French naturalist Charles Bonaparte.

[9][10] The English name "Savannah sparrow" was introduced in 1811 by the Scottish-American ornithologist Alexander Wilson in the third volume of his American Ornithology; or, the Natural History of the Birds of the United States.

[13] Seventeen subspecies (including the large-billed sparrows) are currently recognized, though many are only described from wintering birds and much of the variation seems to be clinal.

[15] There are two dark, large and strong-billed subspecies: Belding's (Savannah/large-billed) sparrows are all-year residents of salt marshes of the Californian Pacific coast.

The variation generally follows Gloger's rule, with Alaskan and interior races the palest, and southwestern coastal forms the darkest.

The general pattern of variation has a fairly clear divide, southwest of which the birds become notably darker; this agrees quite well with the limit between P. sandwichensis and P. (s.) rostratus.

[17] This passerine bird breeds in Alaska, Canada, northern, central and Pacific coastal United States, Mexico and Guatemala.

They are typically encountered as pairs or family groups in the breeding season, and assemble in flocks for the winter migration.