The Leventhal map center at the BPL takes a trip out West

An 1844 “Map of North America Denoting the Locations of the Various Indian Tribes,” by James Bowden.Courtesy of BPL

The United States began in 1776. So far, so good. Actually, not so far: With very few exceptions, its newly minted citizens lived along the Atlantic Coast or within a few days’ journey of it. European settlement of what would become the United States had begun more than 150 years earlier and still barely reached into the continent. Blame the Appalachians. Within a few decades, the mountain range would be breached, and the number of states rise from 13 to 33. One of them, California, was on the Pacific. What had been a coastal sliver now extended from coast to shining coast.

“America Transformed: Mapping the 19th Century — 1800-1862, the US Expands Westward” looks at that period of furious expansion. It runs at the Leventhal Map & Education Center at the Boston Public Library through October. Part two, “1862-1900, Homesteads to Modern Cities,” will open in November.

Such a subject certainly lends itself to maps, and many are on display. The several plat maps here are studies in functionality. Conversely, an 1864 map from the US General Land Office displays delicate washes of color — rose, buff, various blues — over a depiction of state and national borders. A 1908 map collapses past and present, superimposing on the contemporary United States routes taken by explorers from 1501-1844.

Among those explorers are Lewis and Clark. An 1806 map derived from the expedition records the location of Native American villages. Native Americans are a major element in the show. An 1837 diagram of the upper Mississippi and Missouri rivers was drawn by an Ioway chief. An 1844 map shows missionary efforts among Native Americans by the Society of Friends, juxtaposing the locations of Quaker Yearly Meetings and tribal regions.

Much of the show coincides with the period that saw the rise of “manifest destiny.” That concept explicitly described, and implicitly justified, US expansion. Like any good slogan, it obscures complex questions even as it provides a simple answer. Manifest to whose way of thinking? More important, how might you define “destiny”? Most important, whose destiny, exactly?

The acknowledgment of Native Americans helps insure against a triumphalism that celebrates westward expansion and American moral superiority. So does the acknowledgment of African-Americans. A map from 1861 shows the size of slave populations in Southern and border states. Also from that momentous year, “A Map of the Cotton Kingdom and Its Dependencies in America” reaches beyond any one region, noting the impact of King Cotton on Northern mills. America may or may not have been home of the brave. It was only in part — which is to say not at all — land of the free.

Expansion didn’t just mean heading west. There was expansion as infrastructure, as we’d now call it. A map from 1796 shows post roads, the information superhighway of the day. The show includes a map of Lowell, which wasn’t incorporated until 1826. That was only 11 years before the incorporation of Chicago. There are two maps of that city, from 1834 and 1863. The latter measures 75 inches by 44½ inches: the City of Big Shoulders as City of Big Maps.

Some of the more interesting items aren’t maps. There are prints and rudimentary examples of informational graphics. A chart showing population rankings of US cities decade by decade from 1790-1890 is notably handsome.

Maps need more than terrain and abstract reasoning to exist. They require tools. The show includes a surveyor’s compass, chain, and chain pins. Expansion involves money as well as mileage There are not one but two stock certificates in the show (one each from the Baltimore & Ohio Railroad and the Lancaster Turnpike, in Pennsylvania). The show includes three Erie Canal cargo tickets, and four promotional cards for clipper-ship lines sailing to California. The presence of these items reminds us that not just geography, but technology, economics, demographics, and politics have an important place in understanding America’s spatial transformation.

In a nice touch, the Leventhal Center places the world at visitors’ feet — or at least renderings of several North American parts of it. Several maps have been superimposed on the floor. America looked west during these years. Visitors should remember to look down.

AMERICA TRANSFORMED: Mapping the 19th Century — 1800-1862, the US Expands Westward

At Leventhal Map & Education Center at the Boston Public Library, Copley Square, through October. 617-859-2387, www.leventhalmap.org