Captain America: Sentinel of Liberty #8-9
Or, the first time Sam Wilson was Captain America. While this was published in the late 90s, the story actually takes place in Sam’s early days as the Falcon – no wings, still wearing the green costume from Exile Island. This would seem to put it somewhere between Captain America vol 1 #134 to #143, in the period where the comic is titled Captain America and the Falcon but before the cover art switches to the new white and red design for him. But really it could be set at practically any time in the last 50 years. This is an issue that isn’t going anywhere fast, and that’s one of the things that sadly helps the weird Marvel stretch time work. Comics that were published in the 60s become “a few years ago” in the 80s; at the moment I’m saying that Sam and Steve have been working together for about 15 years.