What does James learn about Jim Crow laws on his trip to town?

The Jim Crow laws are presented in a very understated way in the story. James is in town with his mother, Octavia, for a simple dental appointment. Yet on their journey, they encounter a number of obstacles related to the legal apparatus of racism that existed at that time. When he gets on board a bus at Bayonne with his mother, James notices that the vehicle is racially segregated:

When I pass the little sign that say ‘White’ and ‘Colored,’ I start looking for a seat.

Even at such a young age, James understands the power that "they" have, a power that forces him and his mother to sit at the back of the bus while white people sit at the front:

They got seats in the front, but I know I can’t sit there, ’cause I have to sit back of the sign.

Not just man-made vehicles, such as buses, but also features of the natural world are segregated, as James notices when he looks out at the river:

[t]hey got pool-dos on the water.

In this segregated society, white people own everything, even a body of water on which rich people ride their boats.