Growth improved from the 1.3 percent rate in the April-June quarter, the Commerce Department said Friday.
The pickup in growth may help President Barack Obama's message that the economy is improving. Still, growth remains too weak to rapidly boost hiring. And the 1.74 percent rate for 2012 so far trails last year's 1.8 percent growth, a point GOP nominee Mitt Romney will emphasize.
The report is the last snapshot of economic growth before Americans choose a president in 11 days.
The economy improved because consumer spending rose 2 percent in the July-September quarter, up from 1.5 percent in the second quarter. Spending on homebuilding and renovations increased more than 14 percent. And federal government spending expanded sharply on the largest increase in defense spending in more than three years.
Growth was held back by the first drop in exports in more than three years and flat business investment in equipment and software.
The economy was also slowed by the severe drought this summer in the Midwest. That sharply cut agriculture stockpiles and reduced growth by nearly a half-point.
The government's report covers gross domestic product. GDP measures the nation's total output of goods and services - from restaurant meals and haircuts to airplanes, appliances and highways.
The first of three estimates of growth for the July-September quarter sketched a picture that's been familiar all year: The economy is growing at a tepid rate, slowed by high unemployment and corporate anxiety over an unresolved budget crisis and a slowing global economy.
While growth remains modest, the factors supporting the economy have changed. Exports and business investment drove growth for most of the recovery, but are now fading. Meanwhile, consumer spending has ticked up and housing is adding to growth after a six-year slump.
Consumer spending drives nearly 70 percent of economic activity.
Businesses have grown more cautious since spring, in part because customer demand has remained modest and exports have declined as the global economy has slowed.
Many companies worry that their overseas sales could dampen further if recession spreads throughout Europe and growth slows further in China, India and other developing countries. Businesses also fear the tax increases and government spending cuts that will kick in next year if Congress doesn't reach a budget deal.
Since the recovery from the Great Recession began in June 2009, the U.S. economy has grown at the slowest rate of any recovery in the post-World War II period. And economists think growth will remain sluggish at least through the first half of 2013. Some analysts believe the economy will start to pick up in the second half of next year.