The mountain in "The Negro Artist and the Racial Mountain" is considered as an obstacle for Negro artists who wish for others to recognize their work. This isn't just part of their job, but it's part of a racial dispute because of their color. Langston Hughes, the author, describes these Negro artists as very talented people. These are also people who believe they can make it big as artists, but they wish to be white to do so. Black artists think they can't be accepted as people, let alone artists. So the mountain in the essay represents a huge obstacle these people have to achieve. That obstacle is being accepted by everyone else, and that includes them looking past their color before appreciating their art.
The line is often referred to as the "line of best fit", this line is drawn so that more accurate conclusions can be drawn from given data. This has numerous uses across the sciences.
