A few quick notes on the film;
Director Hayao Miyazaki
is a renowned animation director in both Japan
and the U.S. Mononoke, released in 1997, quickly became the highest-grossing Japanese film of all time. It spent eight months (!) in theaters, and grossed
$150 million in a country with only a tenth of the theaters
that the U.S. has.
The film itself was in development as early as 1980, when Miyazaki began to sketch out the original character for San. The underlying man-versus-nature theme of Mononoke also permeated an earlier Miyazaki film, Nausicaa. However, he was still intent on creating a film with Mononoke's character, and in 1994, production on Mononoke Hime began.
Part of the reason for the film's success was it's 'genre-busting' appeal. Unlike most period dramas, he gave his samurai and geishas deeper and more human characterizations.
Mononoke was Studio Ghibli's first computer-animated film, and so they spent 19.2 million dollars on the necessary hardware and software to produce it. Miyazaki himself took a hand personally in 80,000 (!) cels over the course of the movie.
The grueling workload and the huge expense paid off, though, as Mononoke is widely considered to be the film of the decade.
--Research source: "Princess Mononoke: The Art and Making of Japan's Most Popular Film of All Time"