The Strange Maps website has an interesting chart showing where in the galaxy television broadcasts from the United States currently are floating about starting with President Roosevelt’s speech opening the 1939 New York World’s Fair (on April 30th, 1939) and the first televised baseball game (on May 17th, 1939). Both programs were broadcast by NBC’s experimental W2XBS station from New York City. The opening of the 1939 New York World’s Fair kicked of regular television broadcast in the United States. Read more about that here.
The question on my mind is whether the signal strength of television broadcasts today, let alone during the 1940s, is sufficient to actually reach even the closest star (Alpha Centauri). Strange Maps notes that this may not be possible and some of the comments suggest that past Pluto television broadcasts will have degraded into nothingness. But there’s always the chance that some alien civilization has received, recorded and enjoyed programs like Mary Kay and Johnny or Hour Glass. Now we just have to wait until they come visit Earth, bringing with them these no-longer-lost shows.