This is Heade's Newbury Marshes (c. 1871) from the John Wilmerding Collection. Newburyport, MA lies on the coast 40 miles north of Boston, at the mouth of the Merrimack River.
In those days, salt marshes were used for cattle grazing, and salt hay was harvested for winter fodder. Over the past 100 years, the once-vast Atlantic coast salt marshes have been devastated by fill, development, and by channelization in the early 1900s in an effort to reduce mosquitoes (Malaria was a big problem in New England at the turn of the century.) In one of the coastal New England towns I grew up in, the salt marsh acreage dropped from 1000 acres to 30 acres, mostly since 1940.
I think the subject of Salt Marshes will need to be a future post.