Because of his extensive theoretical and practical work, he is considered the founder of modern town planning as a discipline, having coined the word "urbanization".

When the government of the time finally gave in to public pressure and allowed Barcelona's city walls to be torn down, he realized the need to plan the city's expansion so that the new extension would become an efficient and livable place, unlike the congested, epidemic-prone old town within the walls. When he failed to find suitable reference works, he undertook the task of writing one from scratch while designing what he called the Ensanche or Eixample, borrowing a few technological ideas from his contemporaries to create a unique, thoroughly modern integrated concept that was carefully considered rather than whimsically designed