Click here for an illustrated timeline of the fifth century
Date:  431/430 BCE, end of the first year of the Peloponnesian War

Key items to keep in mind:

The polis:  Athens is a city-state, with possibly 140,000 residents in all and 50,000 citizens (all of these were adult free males)

The War: it had just erupted, between Athens and Sparta and their allies, for a host of causes of which the underlying one was Sparta’s "fear of the growing power of Athens" (Thucydides 1.88.1, 118.2).

The Athenian Empire, or Delian League: Athens had become leader of a defensive alliance of Greek states set up after the Persian invasion of Greece (480-479 BCE) and had gradually consolidated her leadership, reducing the ability of individual member states to command independent naval forces, and taxing them instead to support ship-building at Athens.  At its peak the Empire had about 247 member states, most of them east of Athens: northeast as far as Chalcedon in the Black Sea, southeast as far as Aspendos, more than 400 miles away on the south coast of what is now Turkey.  Athenian ambitions moved even further east—to cyprus, to Egypt (which she failed to conquer in the 450s)—and west (to Sicily).

The navy, democracy, empire and slavery:  a maritime empire required reliance on a navy crewed (partly) by lower-class citizens, who naturally expected a commensurate role in state policy making. By the 430s, every citizen of whatever wealth status had a right to vote, and nearly all offices were determined by lot.  Citizenship became increasingly precious.  Concomitant with this came an chattel slavery and an increasing inclination to expand the empire.

Athenian wealth: a major source of Athenian wealth from the 480s was the silver mines at Laureion (on the east coast of Attica).  There is some dispute over how much Athens profited from the Empire, but she clearly did prosper in this period, and became a center for commerce of all sorts.
 

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