The overall Life Evaluation Index score Gallup found for March was 49.9, compared with 49.6 in January and 50.1 in February.
Those numbers are a significant uptick from October 2011 when the score bottomed out at 46.8.
The score, which Gallup first began using in 2008, started moving up in November.
"These ratings coincide with growing confidence in the economy, rising U.S. satisfaction, and improving standard of living perceptions, Gallup said in a statement.
Gallup divides the population into thriving, struggling and suffering segments. In March, 53.3 percent were thriving, 43.4 percent struggling and 3.4 percent suffering, percentages that had changed little.
The numbers come from data gathered March 1-31 for the Gallup-Healthways Well-Being Index survey. The margin of error for the entire sample is 1 percentage point.