Which program did PBS use to attract its first significant audiences?

PBS used "Sesame Street" to attract its first significant audiences due to the show's innovative approach to children's education and its ability to merge entertainment with learning effectively. Launched in 1969, "Sesame Street" was groundbreaking in its use of a format that included a mix of live-action, puppetry, and animation, which captivated young viewers and their parents alike. The show's focus on literacy, numeracy, and social skills, incorporated into engaging and memorable segments, helped to establish PBS as a key player in children's programming.

The show's immediate popularity and its continued relevance over the years contributed significantly to the growth of PBS's audience, making it a cornerstone of educational television in America. Additionally, the success of "Sesame Street" allowed PBS to expand and develop other educational programming, setting the standard for quality children's content on public television.