Harappa shares its name with the civilization it was part of. Both cities were part of the Harappan civilization.
Harappa was around much earlier and much longer. Evidence points to it being founded around 3300 BCE and being in existence for about 2000 years. Archaeologists name five periods of Harappa:
Ravi Aspect of the Hakra phase, 3300–2800 BCE; Kot Dijian or Early Harappan phase, 2800–2600 BCE; Harappan Phase, 2600–1900 BCE; Transitional Phase 1900–1800 BCE; and finally, Late Harappan Phase, 1800–1300 BCE.
By contrast, Mojenjo Daro was built around 2600 BCE and was already abandoned around 1900 BCE, lasting about 700 years. Archaeologists uncovered remains of it in 1919.
Harappa still has a modern day village less than a mile from the archaeological site. It was a railway center under British colonial rule. Archaeologists began uncovering the ruins earlier, in 1826.