Final answer:
The third 'J' who died of a drug overdose in the acid rock era was Janis Joplin. Along with Jimi Hendrix and Jim Morrison, they symbolize the intersection of cultural and political shifts during that time period. Their deaths marked an end to the 1960s' idealism, overshadowed by the turbulence of the 1970s.
Step-by-step explanation:
The three J's that died of drug overdose in the acid rock era were Jimi Hendrix, Jim Morrison, and Janis Joplin. These cultural icons, including Hendrix and Joplin who both died in 1970, epitomized the highs and lows of American popular culture during a time of significant political and social upheaval. The idealism of the 1960s gave way to a more cynical outlook in the 1970s amidst events such as the Vietnam War, Watergate, economic challenges, and the Iranian hostage crisis.
The art piece 'Jimi Hendrix' by David Herrera, cast in bronze by Daryl Smith and displayed at Broadway and Pine in Seattle, serves as a tribute to one these influential musicians. The legacy of these artists remains a poignant reminder of the era's struggle between progress and the harsh realities that challenged America's narrative of continual advancement.