That's up from 60 percent in 1993-94, the Centers for Disease Control and Prevention said.
"It looks like it is an all- time high" based on CDC surveys since the mid-1980s, said Jeff Lancashire, a CDC spokesman.
Experts attributed the rise to education campaigns that emphasize that breast milk is better than formula at protecting babies against disease and childhood obesity. A changing culture that accommodates nursing mothers might also be a factor.
The percentage of black infants who were breast-fed rose most dramatically, to 65 percent. Only 36 percent were breast-fed in 1993-94, the new study found.
For whites, the figure rose to 79 percent, from 62 percent. For Mexican-Americans, it increased to 80 percent, from 67 percent.
Former U.S. Surgeon General Dr. David Satcher celebrated the report's findings, noting that black women have historically had lower breast-feeding rates.
"It was very impressive that when it comes to beginning to breast-feed, African-American women have had the greatest progress," said Dr. Satcher, who is an administrator at Atlanta's Morehouse School of Medicine.
The report is based on a comprehensive federal survey involving in-person interviews and physical examinations. The findings are based on information for 434 infants from the years 2005 and 2006.
A telephone survey of thousands of families, released last year, found that 74 percent of infants in 2004 had been breast-fed.
At least three types of CDC surveys have shown breast-feeding rates moving upward since the early 1990s, officials said.
The latest CDC report found rates of breast-feeding were also lowest among women who are unmarried, poor, rural, younger than 20, and have a high school education or less.