Context: The novel The Grapes of Wrath is synonymous with the Great Depression.

veracity - n. - Devotion to the truth; truthfulness.

Context: Although The Grapes of Wrath is fiction, when it was published, its veracity stirred public opinion.

vigilante - n. - A self-appointed doer of justice.

Context: The migrant workers of the Depression were often the victims of violent vigilante groups who resented their presence.

gingham - n. - A yarn-dyed cotton fabric woven in stripes, checks, plaids, or solid colors. 

Context: The woman wore a gingham dress to the ball.

insubstantial - adj. - Negligible in size or amount.

Context: Two pounds of food is insubstantial for the winter.

arable - adj. - Fit for or used for growing crops.

Context: The great drought of the early 1930s and the windstorms that followed turned formerly arable land into dust.
derisive - adj. - Expressing or showing contempt or scorn.

Context: The uprooted people of the Dust Bowl were called by the derisive name Okies.
harrowing - adj. - To bring trouble, distress, or agitation. 

Context: Steinbeck describes the experiences of most of the migrant families as harrowing; there seems to be no end to their struggles and hardships.
indigent - adj. - Suffering from indigence; impoverished.
Context: The hard working farmers of the Dust Bowl, some of whose families had lived on the same land for generations, became indigent after they lost their homes.

migrant - n. - A person who moves regularly to find work, especially harvesting crops.
Context: The life of the migrant farmer is dictated by the cycles of planting and harvesting.

insinuation - n. - The act or process of insinuating; a creeping, winding, or flowing in.
Context: His voice had the same quality of secrecy and insinuation his eyes had.

judiciously - adv. - In a judicious manner; with good judgment; wisely.

Context: The driver squinted judiciously ahead and built up the speed of the truck a little.

proboscis - n. - A long flexible snout or trunk, as of an elephant.

Context: That proboscis is a nose-like.

meerschaum - n. - A fine white claylike mineral, soft, and light enough when in dry masses to float in water.
Context: The skin was as brown as meerschaum.

lithely - adv. - Readily bent; supple

Context:  He swung his leg over and dropped lithely to the ground.

incredulously - adv. - Expressive of disbelief

Context: The man gave me a stare incredulously.

dwindling - v. - To become gradually less until little remains.

Context: The fire dwindled in an hour.

scrounging - v. - To obtain by salvaging or foraging; round up.

Context:  The sound we had heard was ear-scrounging.

pauper - n. - One who is extremely poor.

Context:  The homeless man seemed to be a pauper.

exhortation - n. - The act of practice of exhorting; the act of inciting to laudable deeds; incitement to that which is good or commendable.
Context:  And now gradually  the sentences of exhortation shortened, grew sharper, like commands.