Jean-François Millet’s painting, Man With a Hoe, depicts an exhausted peasant man working in a field. It was meant to highlight the plight of the working class and was considered very controversial at the time. Inspired by this painting, Edwin Markham wrote the poem “The Man with the Hoe.” Markham’s poem describes a hopeless laborer who is treated more like a beast than a human being.
Markham depicts a man in his poem "The Man with the Hoe" who works the land in an exhausted state--so exhausted, in fact, that he is "brother to the ox." The man at the center of Markham's poem lives much the way a beast of burden would, as he is constantly working and never able to take time to think or to ponder the marvels of the universe.
Markham was inspired to write the poem by the painting L'homme à la houe by Jean-François Millet. This painting, painted in 1860-1862, was controversial when it was shown at the Salon of 1863. It was considered too socialist in its message. The image is of a man whose facial features have been blotted out, obscuring his individuality. Wearing a loose-fitting white tunic, he leans against his hoe in a posture indicating exhaustion. He is working the desiccated land, which is rocky and infertile. The land is brown, and nothing green is growing. In the background, brush fires smolder, suggesting a land that is dried up and unable to yield crops.
There are two answers to this question--two related answers, that is.
The first is that in this poem Edwin Markham is responding to a painting:
“L’homme à la houe” by Jean-François Millet, which means "man with a hoe." You can see this image at the Getty Museum, or via its website. (There's a link below.) In that original painting, you can see that the man with the hoe is tired. He's using the hoe, but he's also leaning on it. His mouth is open, like he's been working hard and needs to pant to catch his breath. While there are other people in the distance, this man is essentially working along.
The second image is the one described in the poem, which goes into more detail and offers specific interpretation. Markham describes things that aren't literally visible, like the first line "Bowed by the weight of centuries..." (How do you show centuries, rather than a tired person?) Markham's literal description is the same: the man, bent over the hoe, mouth open, tired from work. But he adds context, so that most of the poem is actually a political and philosophical argument.