@lovealot - It seems like the acts of sedition and treason were much more common during the Revolutionary War and the Civil War. There were many gatherings and secret meetings in homes where there were discussions about joining the rebels or being loyal to England. And before and during the Civil War,northerners were siding with the south and vice versa.
During both wars, there were treason activities, each side helping someone on the opposite side,defying their government. I don't know how many of these cases were discovered and prosecuted.
During the 1950s, when our government was terrified of communism, the government watched closely for sedition, where there was serious threats of communism seeping into the country.