Final answer:
William Cullen Bryant was around 17 years old when he wrote the poem "Thanatopsis" in 1811.
Step-by-step explanation:
William Cullen Bryant wrote "Thanatopsis" when he was just 17 years old. The poem was published in 1817 and showcased a remarkable depth of thought and maturity for someone of his age. "Thanatopsis" is a meditation on death and the interconnectedness of humanity with nature. It remains one of Bryant's most well-known and influential works, establishing him as an important figure in American literature. His ability to articulate profound reflections on life and death at such a young age contributed to his reputation as a talented and thoughtful poet.