The speaker begins with a somewhat ambiguous opening phrase: "Pile on the Black Man's Burden." This is an abrupt way to start the poem, especially since the line is end-stopped, giving it a terse, declarative sound. Because this line sounds so decisive, it almost functions like a thesis statement of sorts, one that tells readers to add to the hardships that Black people already face in the U.S.
As the poem progresses, it will become increasingly clear that the speaker is actually addressing the powerful white leaders of the U.S., ultimately doing this as a way of highlighting the racism that lies behind certain ways of governing. At this point, however, it's not yet clear why, exactly, the speaker wants to "pile on" the hardships of Black people.
Nevertheless, the speaker continues in line 2 to point out that the oppression of Black people is the "nearest" problem, meaning that it is quite immediate because it's a constant, everyday issue in the U.S. In this way, the speaker begins the poem by calling attention to the fact that Black people in the U.S. are forced to deal with racism and intense hardship. The speaker implies that this is something that the country (or the government, rather) takes for granted and even overlooks, which is why the speaker argues throughout the poem that any new acts of oppression will simply add to the country's ongoing history of racism. In other words, the nation's racist white leaders don't need to look far to find deep-seated issues of racism and turmoil, since these issues exist in a major way in the U.S.
The phrase "the Black Man's Burden" is an allusion to a poem by Rudyard Kipling called "The White Man's Burden." In this poem, Kipling makes the racist argument that the U.S. should embrace imperialism, which is the policy of conquering other nations using diplomatic or militaristic force—a policy historically enacted by powerful white governments to oppress nonwhite populations. Kipling's poem maintains that the U.S. has a moral duty to introduce a so-called civilized lifestyle to nonwhite people. More specifically, Kipling wanted the U.S. to colonize the Philippines, a viewpoint connected to the onset of the American-Philippine War of 1899.
By using the phrase "the Black man's burden," the speaker of this poem makes a pointed reference to Kipling's problematic argument, essentially suggesting in an ironic, sarcastic way that the country might as well take its racist, imperialist foreign policies and add them to the oppression of Black people in America.
These first two lines also establish the poem's use of iambic trimeter. A line of iambic trimeter includes three iambs, which are metrical feet made up of an unstressed syllable followed by a stressed syllable. However, the odd-numbered lines (which are also the non-rhyming lines) include feminine endings, which means they have an extra unstressed syllable that comes after the final stressed syllable. As such, the first two lines look like this:
Pile on the Black Man's Burden.
'Tis nearest at your door;
This meter perfectly matches the meter found in Kipling's "The White Man's Burden," providing readers with yet another indication that this poem is a direct response to Kipling's.