Tom Laughlin and Delores Taylor kept the mailbags brought into the Senate at the finale as souvenirs. They used them for duffel bags on skiing trips. The bags were confiscated by airport officials, claiming that they were property of the US Post Office, but they were actually created for this film.
Tom Laughlin offered James Stewart, who had starred in Mr. Smith Goes to Washington (1939), the Claude Rains role, the corrupt Senator whom Smith had once admired. Stewart declined.
The showing on 4/16/77 in Los Angeles was a sneak preview, and another sneak was held the next night at the Admiral Theatre in Omaha, NE. The North Central edition of "Boxoffice Magazine", dated 5/2/77, had an article about the Omaha showing.
The film mentions the Three Mile Island nuclear accident, that accident occurred on 3/28/79. The film was released 4/16/77. This seems to confirm that the dialogue was changed after initial release to make the filibuster scene appear more relevant.
Contrary to popular belief, this film had a traditional theatrical run. It played in the Milwaukee market for three weeks in November 1977, promoted as a pre-release engagement. After it failed at the box office, it was shelved until its 2004 DVD release.