Also important to the growth of Monte Águila as a city was the construction of the branch line between it and the Polcura River. The trans-Andean railway, whose construction began in 1905, was funded by Porfirio Ahumada, a Chilean national, and his partners Corsini, Carlos Viel (engineer), Martin Worman and Horacio del Río. This was a key event in the formation of Monte Águila, enabling the city to come together and achieve rapid growth, bringing with it social and cultural development. As of 1979, the entire area located west of Río Claro passes to the administration of the Yumbel , while the towns of Monte Águila, Charrúa, Chillancito and Salto del Laja are integrated into the commune of Cabrero, thus structuring the communicate as it is known today. Monte Águila is currently a growing city. In 2002 its population reached 6,090 inhabitants. A large part of the people who live in this town work as a farmer, or work in certain jobs in nearby cities, especially Los Angeles and Concepción, regional capital. At present, the railway industry is in disuse, and much of its structures have been abandoned, this because they are owned by Empresa de los Ferrocarriles del Estado, which prohibits the Municipality of Cabrero or any private entity from taking over these structures. Recently it has been used as a concert stage, and as a mini playground for children. The city has built new businesses and places of recreation, being one of the most remarkable remodeling of the main square of the city. The city is located in the Intermediate Depression, 19.67 km (12 mi) from the Ñuble-Biobío regional boundary. The altitude of the town is 115 m a.s.l.  Due to its location in the Pacific Ring of Fire, much of Chile has been affected by seismic natural disasters. Those that most affected the city were the earthquakes of 1960, and that of 2010, which caused a series of damages. Other catastrophes have affected the town recently, including a , and a large flood, due to heavy rainfall in July 2019. The town has a Mediterranean climate, with very marked seasons and dry and rainy periods of similar duration. The city has been affected by phenomena related mainly to pollution caused by bad odors. One of the most recognized cases relates to the expansion of a liming and wastewater treatment plant, belonging to the Essbio company, through its Biodiversa subdivision.