The plain or the prairie are the symbols of unlimited, happy, rich and borderless space. Always portends better access to wealth and happiness.
Dream dictionary: Plain, prairie dream meanings
…For a young woman Dreaming of crossing a plain, denotes that she will be fortunately situated, if the grasses are green and luxuriant | if they are arid, or the grass is dead, she will have much discomfort and loneliness. See Prairie….