Dee thinks that Mama and Maggie do not understand or appreciate their heritage because they routinely use the family items that Dee thinks should be preserved. First, she marvels over the rump prints in the benches that her father made when they were too poor to buy chairs. Then, she insists that she wants Grandma Dee's butter dish (even though she doesn't want to keep her name, same as her grandmother's), then the churn top and the dasher: all of which Mama and Maggie still use in daily life.
The Great Depression happened in the 1920's and 1930's due to many economic disasters such as the Market Crash in 1929 and bad mistakes by the President (Hoover)