Now housing the Hansen Planetarium, this building originally housed the Salt Lake City Public Library. It was constructed in 1905 with oolitic limestone from the Green River Formation.

PI-60 Building Stones of Downtown Salt Lake City, A Walking Tour

15 South State Street

The Hansen Planetarium was built in 1905 of Sanpete oolitic limestone from the Green River Formation, quarried east of Ephraim in Sanpete County along the base of the Wasatch Plateau. This unique limestone was deposited during the Eocene Epoch (55 to 38 million years ago) in a large freshwater lake and is composed of tiny oolites.

An oolite is a small, rounded grain, made up of concentric layers of calcium carbonate that precipitated around a nucleus, usually a mineral fragment or small shell. Oolites form in shallow, wave-agitated water, gradually accumulating more and more layers.

An oolite cross section depicting an onion-like structure of calcium-carbonate layers surrounding a tiny shell or mineral fragment.

This decorative building originally housed the Salt Lake City Public Library and included a children's library and a small auditorium for meetings of the League of Women Voters and fine arts organizations.

Mining millionaire John Quackenbos Packard donated both the site and the construction funds provided that the city would maintain and keep it as a library. In 1964 the library outgrew its space and was moved to its present location east of the City and County Building. The old library building now lodges the Hansen Planetarium and includes a space science library.

Sanpete oolitic limestone was also used for the Kearns Mansion at 603 East South Temple (also known as the Governor's Mansion) and for the intricately carved facade of Hearst Castle at San Simeon, California.

Oolitic limestone being quarried and shipped from a quarry near Ephriam in Sanpete County. (Unknown date, possibly early 1900s.)
Photo courtesy of the Utah State Historical Society.

Continue south down State Street to the glass-enclosed Social Hall Heritage Museum. Enter and descend to the lower level.

(On Sundays, both the Social Hall Heritage Museum (#12) and the ZCMI Center Mall (#13) are closed. To skip these stops and reach the Utah Commercial and Savings Bank (#14), continue south along State Street to 100 South, cross to the southwest corner of the intersection, then walk west along 100 South until you reach 22 East 100 South.)

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