Just in time for Pioneer Day, a New York City company is marketing high-quality reproductions of a map that Brigham Young used in the historic trek west.

"A New Map of Texas, Oregon and California" was published in Philadelphia in 1846 by Augustus Mitchell. It's often called "the Mitchell map."

"This was an extremely important map," said Ron Bitton, curator of historical maps and newspapers at the Western Americana Special Collections, Marriott Library, University of Utah.

The Mitchell map was widely distributed, and people making the westward trek depended on it heavily, he said. It also was important in history because the way Mitchell drew boundaries influenced action during the Mexican War of 1846-48.

The main distribution of the 21-by-22-inch map showed the West in muted, hand-colored tones. "It was originally sold in a small green leather folder and had a 46-page supplement" with descriptive information, Bitton said.

Brigham Young bought or had one of his associates purchase a dozen copies for use during the trek that ended with the settlement of Utah in 1847, noted Richard Sandhaus, owner of DiscoveryEditions.com, which is selling the reproductions. (That purchase was confirmed by other references also.)

Sandhaus said DiscoveryEditions makes high-quality copies of what they consider "the art of discovery, 16th to 19th century rare maps." The company also reproduces early botanical and wildlife images, such as bird prints by John James Audubon.

Skilled map collectors and appraisers can't tell the reproductions from originals, he said — until they flip them over. Then they can see the repros are printed on modern paper.

Not only does the paper feel different from old documents, but the company stamps and puts edition numbers on the back, identifying them as copies.

"But if you put them on a frame hanging on the wall, you could not possibly tell the difference," Sandhaus said.

Reproductions sell for $1,150, although an auction to help the Trust for Public Land is offering one that may go for less. The auction is sponsored by DiscoveryEditions, which has pledged to help organizations like the trust.

The reproduction Mitchell Map that is being auctioned is on view at the Hotel Monaco in downtown Salt Lake City. The auction concludes Aug. 1.

Made by proprietary technology, the maps look so much like early ones that they even retain the fold markings. A view of the Mitchell Map is posted by DiscoveryEditions at www.discoveryeditions.com.

Sandhaus said he acquired the rights to reproduce the map from a New York City expert he called the world's leading rare map dealer. "If you were going to choose four or five maps that tell the story of America, of coming across east to west, this (the Mitchell map) in a way would be the punch line."