In the late 1700s classical guitars were fairly small. The early 19th century saw an increase of interest in the guitar thanks to two big names: Fernando Sor and Mauro Giuliani.
Fernando Sor was a great influence on the guitar in the interim between the late eighteenth and first quarter of the nineteenth century. His compositions and performances, as well as his Method for the Spanish Guitar, played a key role in the development of the guitar technique. He was also responsible for raising the integrity of the guitar to a concert instrument.
The other leading exponent of the guitar at that time was Mauro Giuliani. Giuliani began his musical studies on the cello, but he was soon drawn to the guitar. After the debut of his Concerto Op.30 for guitar and orchestra, he was declared the greatest guitarist alive and his fame spread all over Europe. When in Vienna, Giuliani played for Ludwig Van Beethoven. The famous composer is reported to have declared that the guitar sounded like "a miniature orchestra."
The guitar experienced great popularity in the early 19th century. Nonetheless, the instrument lost its popularity as the 19th century progressed.