He was of Scottish (English) ancestry.
Toensing and Minnesota Place Names list his birth year as 1825. Lives of the Governors of Minnesota, 1908 lists 1828.
John L. Merriam and his son William Rush Merriam both served as Speaker of the House.
He "was a leading republican of the state." (Burnquist, A.A. Minnesota and Its People, Volume 1. Chicago: The S.J. Clark Publishing Company, 1924, p. 320.)
The Minnesota Legislative Manual, 1871 lists 1859 as the year he came to Minnesota. The Minnesota Legislative Manual, 1870 and Minnesota Place Names lists 1860. Other sources list 1861.
"He came to Minnesota in 1860, settling in St. Paul, where he engaged with J.C. Burbank and Capt. Russell Blakeley in the staging and expressing business. He helped to organize the First National Bank and the Merchants' National Bank of St. Paul and was president of the latter." (Minnesota Place Names, MHS, 2001.)
He came to St. Paul, Minnesota in 1861. (Burnquist, A.A. Minnesota and Its People, Volume 1. Chicago: The S.J. Clark Publishing Company, 1924, p. 320; Minnesota in Three Centuries, 1908, p. 36; Lives of the Governors of Minnesota, 1908, p. 307; Progressive Men of Minnesota, 1897)
The Merriam Park area of St. Paul, Minnesota was named for John L. Merriam and his son, William Rush Merriam.
He died in St. Paul, Minnesota.