After independence, Peru and its neighbors engaged in intermittent territorial disputes.
A short-lived attempt to reunite Peru and Bolivia was made during the period 1836–1839 when the Peru-Bolivian Confederation came into existence, severe internal opposition led to its demise in the War of the Confederation.
Peru embarked on a railroad building program. Henry Meiggs built a standard gauge line from Callao across the Andes to the Interior, Huancayo; striking for Cuzco he built the line but also bankrupted the country.
In 1879, Peru entered the War of the Pacific which lasted until 1884. Bolivia invoked its alliance with Peru against Chile. The Peruvian Government tried to mediate the dispute by sending a diplomatic team to negotiate with the Chilean government, but the committee concluded that war was inevitable. Chile declared war on April 5, 1879. Almost five years of war ended with the loss of the department of Tarapacá and the provinces of Tacna and Arica, in the Atacama region.
Originally Chile committed to a referendum for the cities of Arica and Tacna to be held years later, in order to self determine their national affiliation. However, Chile refused to apply the Treaty, and both countries could not determine the statutory framework. In an arbitrage that both countries admitted, the USA decided that the plebiscite was impossible to take, therefore, direct negotiations between the parties led to a treaty (Treaty of Lima, 1929), in which Arica was ceded to Chile and Tacna remained in Peru. Tacna returned to Peru on August 29, 1929. The territorial loss and the extensive looting of Peruvian cities by Chilean troops left scars on the country's relations with Chile that have not yet fully healed.
Following the Ecuadorian-Peruvian War of 1941, the Rio Protocol sought to formalize the boundary between those two countries. Ongoing boundary disagreements led to a brief war in early 1981 and the Cenepa War in early 1995, but in 1998 the governments of both countries signed a historic peace treaty that clearly demarcated the international boundary between them. In late 1999, the governments of Peru and Chile likewise similarly implemented the last outstanding article of their 1929 border agreement.

Related Links:
Peru Tourism
Trekking Inca Trail
Machu Picchu News