Although in the 17th century in the United States fine art and folk art had similar qualities, a difference between them began to appear as time went on in the 18th and 19th centuries artists with ambition studied abroad and came back to paint portraits  of upper-class families in American society. The less ambitious or less fortunate artists traveled around their own areas and created pictures of countryside society. Anyway, artists got trained and those simple creations improved a lot. Around 1930,folk art began to take on a new meaning and was considered as an expression of a small cultural class. Folk art is never the product of art movements, but comes out of craft traditions. This art is based not on measurements or calculations and rarely goes with the standards of realism. It goes straight to the bases of art which the folk artists feel naturally. The period 1930~ 1960 was the time when folk artists began to receive recognition. They often began their art careers late in life and used art as an outlet  for their energy. Their materials were cheap and simple, their subjects were different, but their creativity flowed. Doing their own things became the norm , and was what made folk art so desirable. Although it is hard to define folk art, one thing is certain --- it touches us in a special way because the artists show us how he or she brought beauty into their everyday life. Since folk artists come from all walks of life, each piece of art created is one of a kind, emphasizing color, simplicity of line and brave, simple form. Most importantly, it exemplifies(...) the history of American life. The author's purpose in writing the text is to   _  .
speak highly of folk art compare folk art and fine art explain the history and characteristics of folk art in America explain the development and changes of American art