This episode's credited co-writer, David Davis, credits Rhoda's oft-quoted chocolate line ("I should just apply it directly to my hips") to staff writer Treva Silverman, who, according to Davis, came up with the line during the dress rehearsal and gave it to producer James L. Brooks.
The first time in the series that Mary kisses a man.
This is one of two episodes of the series in which Edward Asner (Lou Grant) does not appear. The other being Divorce Isn't Everything (1970). He appeared in every episode after Season 1.
The title comes from the rallying cry from the era of the Oregon Territory dispute in the early 19th century to claim territory further into Canada. "54° 40' or Fight!" refers to the latitude in question. It was finally settled on 49°.
On the DVD commentary for this episode, writer David Davis said he and Lorenzo Music had Bob Newhart in mind for the IRS agent and wrote the character's lines for Newhart's voice.