As a sign of commitment to the U.S. market, Porsche is building a new headquarters in Georgia, the auto maker’s top North American executive says today.

The site, in the “Aerotropolis Atlanta” business park near Hartsfield-Jackson International Airport, will consolidate the auto maker’s Chicago-area finance arm and holding-company operations with its current administrative, marketing, parts, service and dealer-training functions in Atlanta.

The investment “sends a strong message to our dealers and our customers that we believe in the strength of the U.S. market and its future growth,” Porsche Cars North America President and CEO Detlev von Platen says in a statement.

Plans for the new headquarters also promise a test track featuring a 1.6-mile (2.6-km) handling circuit, low-friction areas and an off-road course.

Groundbreaking is planned for fall with completion scheduled for second-half 2013. Porsche says the site eventually will be home to some 400 employees, a total that includes a marginal increase from the auto maker’s current North American payroll.

The announcement comes on the heels of strong April sales in the U.S. Porsche deliveries numbered 3,172 in the month, a 74.8% jump compared with like-2010, according to Ward’s data.

Paced by 4,610 Porsche Cayenne sales through the first four months of 2011, the storied brand’s performance was tracking 46.1% ahead of prior-year.

Narrowly beating the 911 2-seater for second spot was the Panamera sedan, which benefits this year from the addition of a gasoline-electric hybrid alternative.