Stanza 1 Summary

Get out the microscope, because we’re going through this poem line-by-line.

Lift every voice and sing,
Till earth and heaven ring,
Ring with the harmonies of Liberty

This poem opens with music. It's about voices singing for, and about, liberty. So from these first few lines, two of the poem's major themes are introduced: music and liberty.
"[T]he harmonies of Liberty" is a phrase that suggests that liberty is a beautiful thing. Harmony is pleasing—our ears go "ahh…" when we hear it. So, by saying that liberty is harmonious, the speakers suggest that it's a good thing. These speakers are on the side of liberty; they dig it. That makes sense to us. How could liberty not be a good thing?
We get a sense of the power of this singing through the imagery of earth and heaven "ring[ing]" with the sounds of voices. This is some powerful music we're dealing with here. It's way stronger than the music blasting through the super-duper high-tech speakers in our bedroom.
The reference to the rising voices in these lines also suggests the power of speech and song. If we ask for freedom loudly enough, if we sing for it, we'll eventually get it. (Hmm, we wonder if that works for everything. Maybe if we sing as loud as we can for lunch someone will bring it to us?)

Let our rejoicing rise
High as the list'ning skies,
Let it resound loud as the rolling sea.

The speakers present the song that they're singing as "rejoicing." This is a happy song. But no, it's not Pharell's "Happy."
As we've mentioned before (check out "In a Nutshell"), this poem was written to commemorate Abraham Lincoln's birthday. Lincoln was the president who ended slavery in America. This poem is a reflection not only of all the hardships that African-Americans have faced in their history, but also of the long way that they've come since slavery.
By saying that their song is a song of "rejoicing," the speakers suggest that there is joy and happiness to be found in their experience and in the progress that they've made—in spite of all the difficulties that they've lived through. Slavery was definitely a difficulty.
In these lines the speakers use a simile in order to give us a sense of just how powerful this song is. The song rises "[h]igh as the list'ning skies" and it resounds "loud as the rolling sea."

Sing a song full of the faith that the dark past has taught us,
Sing a song full of the hope that the present has brought us;

In these lines we get, for the first time, a reference to the very tough history that African-Americans have experienced. This history is a "dark past."
But the speakers suggest that this past isn't all bad. It's taught African-Americans to have faith, to keep believing no matter how dark and depressing things may get.
The speakers say that it's good not to lose faith in the future, because the present shows us that there is in fact hope, no matter how dark our history has been.
We can see a lot of repetition in these lines. "Sing a song full" are words repeated in both lines. In the poetry biz, that's called anaphora.
As well, the repeated S sounds at the beginning of these words is an example of alliteration. For more on the poem's sound, check out "Sound Check."
The word "us" at the end of the line is also repeated. That's important because we'll find that the poem puts a lot of emphasis on collective experience. Words like "we" and "our" and "us" focus attention on a group of people and their shared experiences. What's more, these words indicate that this poem is being spoken (or sung) by multiple speakers. And that's just great with us. We believe in doing things together (hey, aren't we understanding this poem together?).

Facing the rising sun of our new day begun,
Let us march on till victory is won.

"Facing the rising sun of our new day begun" is an example of a metaphor. The speakers use the image of the rising sun and a new day in order to give a sense of new beginnings, or a new and a more hopeful future, one in which the speakers can be completely free. (Of course, we're one of those late risers who doesn't even know what a rising sun looks like.)
Line 10 makes it clear that victory has not been won yet. In 1900, when this poem was written, African-Americans were still struggling for their basic civil rights. In many ways, the same kind of battle for racial equality continues even today.
The words "march on" imply strength and determination. These speakers are determined, they're moving forward, and they're going to "march on" until they get what they want, which is the victory of complete freedom.
One last thing: notice any rhyme going on here? These last two lines rhyme and, looking back, we can see that so do lines 1 and 2, lines 3 and 6, 4 and 5, 7 and 8, and now 9 and 10. For more on how this poem's put together, check out "Form and Meter."