The crate containing was discovered during a hazardous materials collection event at the fairgrounds on Monday, authorities said.
The crate was marked that it was packaged in March 1957, and sheriff's officials said it was originally part of a stash of disaster supplies for a 200-bed hospital, and had been stored at the fairgrounds for decades.
The ether was considered highly explosive, so rather than trying to transport it elsewhere, plans were made to render it safe by creating a counter-charge, according to the sheriff's office.
"The only way to get rid of it is to detonate it," sheriff's Capt. Tracey Stuart said.