The Bountiful Tabernacle, completed in 1863, is the second-oldest tabernacle still standing (the tabernacle in Parowan beat it by one year). It was nearly torn down in the 1970s, but was saved because of the massive protest that erupted when local leaders announced it was going to be torn down.
It hasn't changed much. In the picture below, you'll notice the absence of spires--they had blown off in a wind storm in 1906 and weren't replaced for nearly 50 years.
(Image Source: Utah State Historical Society)