Photo from historyofmormonism.com.
1. The unique Tabernacle roof was designed and built by Henry Grow, a bridge builder. He was asked to span as broad an area as he could without using interior supports. He constructed the roof like a lattice bridge, which vertically distributes the very heavy weight of the roof and keeps the sandstone buttresses in alignment.
2. When first built, the Tabernacle was the largest hall in the world unsupported by columns.
3. The original roof was covered with 350,000 hand-hewn, white pine shingles. It was replaced with copper sheeting near the turn of the century, which was then replaced with aluminum in 1947.
Photo from ldsces.org
4. Before the gallery (the upper seating level) of the Tabernacle was built, the building echoed horribly, and it was hard for the congregation to understand the speakers. The gallery was built with acoustics in mind. A thirty-inch gap between the gallery and the wall gave the Tabernacle the amazing sound quality we all know today.
5. The Tabernacle could originally seat 10,000 people, but at the dedication it was packed to full capacity--around 13,000 people!
6. The benches were made from white pine, which was cheapest and easiest for the early Saints to build with, but they were all hand-painted to resemble oak, which was the preferred (but too-expensive) wood to use.
7. At the dedication of the Tabernacle, George Q. Cannon read the names of 105 people called to leave their homes to serve missions. Imagine having every new missionary called by name at General Conference! It would take weeks!
8. The Tabernacle was originally used as the main meeting area for Salt Lake City residents. Every Saint in the city was invited to go there for Sunday meetings, and speakers were told not to prepare a talk beforehand, but to just speak by the Holy Spirit's prompting.
9. Originally, the Sacrament passed during Tabernacle worship, but as the number of Saints grew, it took most of the two-hour meeting just to pass it around to everyone. This practice was eventually removed from Tabernacle meetings, with Saints encouraged to participate in the sacrament in their ward buildings instead.