In colonial America, a subset of “the people”— those who were male, able bodied, and within a certain age range.
Justice Antonin Scalia, writing for the majority in District of Columbia vs Heller, stated:
Nowhere else in the Constitution does a “right” attributed to “the people” refer to anything other than an individual right. What is more, in all six other provisions of the Constitution that mention “the people,” the term unambiguously refers to all members of the political community, not an unspecified subset. This contrasts markedly with the phrase “the militia” in the prefatory clause. As we will describe below, the “militia” in colonial America consisted of a subset of “the people”— those who were male, able bodied, and within a certain age range. Reading the Second Amendment as protecting only the right to “keep and bear Arms” in an organized militia therefore fits poorly with the operative clause’s description of the holder of that right as “the people”.