PORTLAND — To celebrate 20 years of being on the map, a University of Southern Maine library this week will show off some of its finest and rarest artifacts.

The Osher Map Library and Smith Center for Cartographic Education, at 314 Forest Ave., will showcase some of the gems in its collection in an exhibit called “Masterpieces at USM: Celebrating Five Centuries of Rare Maps and Globes.”

The free public exhibit opens at 5:30 p.m. Thursday, Nov. 19, and will run until March. Space will be limited at the opening; anyone interested should RSVP by calling 780-4850 or online. The Nov. 19 event will have featured speakers, including USM President Glenn Cummings.

The library is open Tuesday, Wednesday and Friday 10 a.m.-4 p.m., Thursday 10 a.m-8 p.m., and Saturday 10 a.m.-2 p.m. It is closed on Sundays and Mondays.

Bob Spencer, vault manager at OML, said the building’s gallery display changes three to four times a year, and there is usually a theme with each display. For the upcoming exhibit, he said the gallery will display “the gems of the collection.”

The collection includes globes dating from the 1600s to the present, a copy of the first atlas ever printed from 1575, and a copy of the oldest printed map, which is a map of Jerusalem from 1475.

Osher Map Library in Portland Marks 20 Years from Sun Media on Vimeo.

“Some of the earliest printed things were maps,” Spencer said.

OML is also digitizing its collection. The library has three camera stations, where photos of each item are taken at multiple positions to create three-dimensional images.

Adinah Barnett, a digital imaging associate at OML, said hundreds of images are taken and then “stitched together” in a post-production program to create the 3-D images with rotating views. The images can be viewed online at oshermaps.org.

“It can take weeks to do the post-production,” Barnett said.

Spencer and Barnett said digitizing the collection allows greater public access. Items in the collection are usually on display behind glass or are too fragile to handle, but the online collection allows people to “see the whole image,” Barnett said.

Spencer said OML’s collection of globes is the second-largest in the United States, bested only by the Library of Congress. Barnett said the effort to digitize the globes isn’t being done anywhere else in the world, calling it “cutting edge.”

“Nobody is doing it quite to the level of detail and artful presentation we are,” she said.

The digitization effort will take years to complete, Spencer said.

OML is a three-story building. The top two floors are vaults for the collection of maps, atlases and globes. The first floor houses the gallery and camera stations. Spencer said there are roughly 450,000 individual objects in the collection, all of which were donated. However, he said, if each image in the library was counted, it’s “in the millions.”

“It’s really amazing,” Spencer said.

He said not everything in the collection is “rare and unusual,” and less valuable items are stored on the third floor. For example, OML has a collection of 40,000 road maps, which are still being indexed. He also said there are guidebooks and modern-day items in the collection as well. There are even shower curtains with globes printed on them.

“It’s still an important part of our collection,” he said.

The second floor contains items from before the 20th century, Spencer said. But even though they are rare items, Spencer said the public can still see them. He said the earliest atlases in the collection come “before the discovery of the new world,” so people can come “walk through time with them.”

“Anybody can come in off the street and see the rarest items in the collection,” he said, adding that making the items available for educational purposes was the intended mission of the library.

Colin Ellis can be reached at 781-3661 ext. 123 or cellis@theforecaster.net. Follow him on Twitter: @colinoellis.

The Osher Maps Library and Smith Center for Cartography Education at the University of Southern Maine in Portland is celebrating its 20th anniversary by displaying some of its rarest items.

Bob Spencer, vault manager at the Osher Map Library in Portland, explains the history behind this map of Jersualem from the year 1475, which he said is the first printed map.

The anniversary exhibition opens Nov. 19 at the library and runs through March.