The 29-year-old Swede, whose uncle played for the 1987 NFL Cleveland Browns, seeks his second PGA title after winning the 2015 Memorial, downing England's Justin Rose in a playoff.
Lingmerth, third at the 2015 National, was one shot in front of a pack on 66 that included Australia's Marc Leishman, South Korean Kang Sung, Canada's Nick Taylor and Americans Troy Merritt, Daniel Summerhays and Johnson Wagner.
"I know I can probably contend here and play well," Lingmerth said. "Feeling great. Had a solid first day, so now it's just a matter of keeping it going."
The par-70 TPC Potomac layout, hosting its first PGA event since 2006, was formidable, with Players Championship winner Kim Si Woo of South Korea shooting 79 a day after his 22nd birthday and defending champion Billy Hurley on 73.
