Who is in charge of managing a construction project?

A contractor or builder is responsible for the day-to-day oversight of a construction site, management of vendors and trades, and the communication of information to all involved parties throughout the course of a building project. In the United States, a contractor may be a sole proprietor managing a project and performing labor or carpentry work, have a small staff, or may be a very large company managing billion-dollar projects. A general contractor is a construction manager employed by a client, usually upon the advice of the project's architect or engineer. General Contractors are mainly responsible for the overall coordination of a project and may also act as building designers and construction foremen (a tradesman in charge of a crew).

Source: Wikipedia