In 1839 Henry David Thoreau and his brother John spent some time exploring the Concord and Merrimack Rivers. A Week on the Concord and Merrimack Rivers was published ten years later, in part as a tribute to John who had died in 1842. The book gathers together close observations and philosophical meanderings. The descriptions of the Merrimack in the early 19th century are poetic and insightful.