''The first shovel full of dirt,'' President Gordon B. Hinckley said Friday.
The 95-year-old Hinckley then grabbed a full-size, gold-painted shovel and cracked, ''And now for the real thing,'' drawing laughter and applause from onlookers.
The new five-story building will be home to church archives, including printed materials, photographs, video and audio recordings. Some of the collection is official church record and some is from outside sources, such as personal journals from members, published materials about the faith from non-church sources and even novelty items such as games with Mormon themes.
The existing collection also includes one of the best-documented records of the settlement of the Western United States, said Richard Turley, managing director of the church's family history department.
In all, the collection holds 3.5 million manuscripts, 210 publications, 100,000 photographs and 50,000 audiovisual records.
Mormons believe Scripture commands them to keep a carefully documented record of church activities and events. Since its founding by Joseph Smith in 1830, the church always has employed the services of at least one full-time historian.
Currently the library is housed in the east wing of the Church Office Building, although the historians' office and archives long ago outgrew the available space, Turley said.
The facility will be built to archival-quality standards, meaning it will be temperature- and humidity-controlled - to about 55 degrees with 35 percent humidity - and tempered lighting to best preserve documents and materials, Turley said.
Security will be tight and although the library is open for public use, not all its pieces will be accessible.
The new building should be open sometime in 2007.