Once Upon a Time in the West ending explained

What happens

Frank kills Morton's men and is lured into a duel with the harmonica player. A flashback shows Frank once made him watch his brother die. Frank dies, Cheyenne dies of his wounds, and Jill brings water to the railroad workers.

The last image

Jill carries water to the men laying track as the railroad reaches Sweetwater, while the harmonica player rides away with Cheyenne's body.

What it says

The gunmen win their private fights and still lose the age they belong to. The railroad arrives anyway, and Jill, who builds rather than kills, carries on. Leone ends the old West with a farewell, not a victory.