Final answer:
The song 'Please Mr. Postman' was notable for being The Marvelettes' debut single, one of Motown's first major hits, and the first Motown song to reach number one on the Billboard Hot 100 chart.
Step-by-step explanation:
The question pertains to the significance of the 1961 song 'Please Mr. Postman' beyond its musical impact. While the information provided about the Great Depression anthem 'Brother, Can You Spare a Dime?' and the history of rural mail delivery is interesting, it does not directly relate to the 'Please Mr. Postman' song. Therefore, to accurately address the significance of 'Please Mr. Postman', one should note that it was the debut single by The Marvelettes for the Tamla (Motown) label and marked one of the first major successes for Motown—a record company that would go on to shape the sound of popular music in the 1960s. Moreover, 'Please Mr. Postman' was notable for being the first Motown song to reach the number one position on the Billboard Hot 100 chart. This marked a pivotal moment in the integration of R&B and soul music into mainstream American pop culture.