Merrimack County's 2026 population is estimated at 159,489, reflecting a 0.51% growth rate over the past year (World Population Review estimate based on U.S. Census Bureau data). Merrimack County is the 3rd largest county in New Hampshire. The 2010 population was 146,395 and has grown 8.94% since 2010.
Data after 2023 is projected based on recent change
Overall: 42.9 years
Female: 43.9 years
Male: 41.8 years
There are 127,310 adults, (31,061 of whom are seniors) in Merrimack County.
Female: 78,240 (50.2%)
Male: 77,727 (49.8%)
The racial composition of Merrimack County includes 90.83% White, and smaller percentages for Black or African American, Asian, other race, Native American, Native Hawaiian or Pacific Islander and multiracial populations.
| Race | Population ↓ | Percentage (of total) |
|---|---|---|
| White | 141,669 | 90.83% |
| Two or more races | 7,862 | 5.04% |
| Black or African American | 2,533 | 1.62% |
| Asian | 2,362 | 1.51% |
| Other race | 1,183 | 0.76% |
| Native American | 259 | 0.17% |
| Native Hawaiian or Pacific Islander | 99 | 0.06% |
Merrimack County 's average per capita income is $59,035. Household income levels show a median of $97,004. The poverty rate stands at 7.64%.
| Name | Median ↓ | Mean |
|---|---|---|
| Married Families | $132,639 | $162,004 |
| Families | $120,007 | $148,618 |
| Households | $97,004 | $123,673 |
| Non Families | $50,960 | $66,353 |
Average Income
Median Household Income
Poverty Rate