I checked census pages. In 1790 NH, there were 32 MORRILL households, and 31 of them were in Rockingham County. By 1800, there were ~70 households in NH. This time there were 40 households in Rockingham County, and 20 households in Hillsborough County, and a few in 3 other counties. (A few more with MORRIL spelling.)
In 1810 the numbers and places were about the same. And no MORRILL households in Merrimack County. By 1820, there were ~90 households in NH, still none in Merrimack County.
By 1860 there were 260 MORRILL people in NH, in about 10 different counties. With 90 of them in Merrimack County.
Betty (near Lowell, MA)