To tell the truth, "The Red Wheelbarrow" was originally untitled. It appears in Williams's collection of poems and prose Spring and All as simply XXII, or number 22. Over time, however, the poem has adopted the title, "The Red Wheelbarrow," and, in our humble opinion, we think this title works.
When we look at a painting, our eye is often drawn to one specific place in that painting, usually because it's particularly juicy or colorful. Check out this painting by Claude Monet, entitled Impression: Sunrise. What do your eyes grab hold of first? We don't know about you, but that little rowboat is pretty interesting. Not to mention that orangey sun. The same is true with "The Red Wheelbarrow" – our eyes can't seem to let go of the image of the red wheelbarrow. The title, "The Red Wheelbarrow," helps to focus our eyes on that red wheelbarrow from the beginning. To us, such a title accentuates the painting-like nature of this poem.