From the Guide to 2010 State and Local Census Geography — Maine — History:

Maine was originally part of Massachusetts. It was included in the Charter of New England in 1620 and the Charter of Massachusetts Bay in 1629; the latter became the Constitution of the Massachusetts Bay Colony, predecessor to the Commonwealth of Massachusetts.

In 1819, Massachusetts agreed to allow its district of Maine to petition for statehood. Maine was admitted to the Union as a separate state on March 15, 1820, as the 23rd state. The state’s boundary with Canada was not formally established until the Webster-Ashburton Treaty of 1842, when Maine assumed generally the same boundary as the present state.

Census data for Maine are available beginning with the 1790 census. Maine was enumerated as a separate district within the state of Massachusetts in the 1790, 1800, and 1810 censuses. Presentation of data as a separate state began with the 1820 census. The population of the legal area of Massachusetts (of which the area of Maine was a part) was 700,745 in 1810; 574,564 in 1800; and 475,327 in 1790.

Data for the legally established state of Maine are available beginning with the 1820 census.

From QuickFacts: statistics for all states and counties, and for cities and towns with a population of 5,000 or more.

Note: The dashboard shown above is cropped at the bottom. Click on the image to see the full dashboard. Click here to see the table view showing the United States; Maine; Portland city, Maine; Lewiston city, Maine; Bangor city, Maine; Augusta city, Maine (state capital).

From data.census.gov — the U.S. Census Bureau's new dissemination platform, replacing American FactFinder (AFF) which will be taken offline on March 31, 2020.

Source: 2018 American Community Survey (ACS), 1-Year Estimates.

From the Statistics in Schools program:

From Census Business Builder: Regional Analyst Edition - 3.0:

From the State Data Center (SDC) Program:

From Foreign Trade > U.S. International Trade Data:

Note: After you create an account, select options for State Export Data (Origin of Movement) or State Import Data (State of Destination) by HS or NAICS. Select State (Maine) and Measures, Commodity, Country and/or Time for data. For more information, see Quick Start Guide.