Edna St. Vincent Millay's "Recuerdo" is a poem about memory. The title is a Spanish word which translates into memory or recollection. The decision to make this the title is obvious, but only if you know the translation. There is nothing in the body of the poem that explains why the title sports the Spanish word for what it is so clearly about. That decision only becomes obvious upon learning that the events of the verse were stimulated by the poet's memory of a visit to Staten Island with Nicaraguan poet Salomón de la Selva. Both were about the same age, both were poets, and both had a revolutionary spirit.
"Recuerdo" becomes a poem about the recollection of a joyous memory that was inspired by the real-life events of an interracial couple. Nothing in the text of the poem indicates this aspect of the couple, but then again, they are not identified in any way. The poem even lacks gender-appropriate (for the time) pronouns. Based simply on the textual content, the participants could just as easily be friends as romantic partners, black as well as white, heterosexual as well as homosexual, or really almost anything.
They are referred to only as "we" by the speaker and that is the point. Every single stanza begins with the same lines: "We were very tired, we were very merry— / We had gone back and forth all night on the ferry."
What they are doing is far less important than that they enjoyed it together as one. If this were a biographical sketch of the same event, it would be a portrait of a white American woman and a Nicaraguan male, and everything would be related to that context of race. Millay is saying none of that matters. It is only at the end that any other person is mentioned. And that person has no reason to care who they are or what they might be to each other. They are customers paying for a newspaper at first. And then they are very nice people who give her them apples and pears and money.
That the poem is given the Spanish title for recollection of a memory is very likely related to her actual companion that inspired the work. It is another way of saying it doesn't matter who the couple is because it is nobody's business. The constant reference to the two as a single entity known only as "we" strongly suggests that it is a poem about how nothing about two people in love or who simply enjoy each other's company should matter to anyone else on the planet except them. One might even term "Recuerdo" a protest poem against prejudice, discrimination, and any argument that may be forwarded that the human species is anything other than just one big collective "we."
