According to Official Guinness Records,
The first selfie was taken by Robert Cornelius (USA) in October 1839, using a daguerreotype technique – an early photographic process employing an iodine-sensitized silvered plate and mercury vapour. Cornelius was required to sit for between three and 15 minutes to allow the necessary exposure time as he posed for the self-portrait in the backyard of his family's lamp and chandelier store in Philadelphia, USA. He wrote on the back of it: “The first light Picture ever taken. 1839.”The Oxford Dictionary recognized "selfie" as 2013's word of the year, defining this as "a photograph that one has taken of oneself, typically one taken with a smartphone or webcam and uploaded to a social media website".Robert Cornelius opened one of the USA’s first ever photographic studios.His daguerreotype is kept at the Library of Congress.The exposure time would have depended on the amount of light in the backyard when he took the picture.
For a complete list of 1839 records, please visit 1839 Guinness Records in United States.