The Maya civilization was a Mesoamerican civilization developed by the Maya peoples, and noted for its hieroglyphic script--the only known fully developed writing system of the pre-Columbian Americas--as well as for its art, architecture, mathematics, calendar, and astronomical system. The Maya civilization developed in an area that encompasses southeastern Mexico, all of Guatemala and Belize, and the western portions of Honduras and El Salvador. This region consists of the northern lowlands encompassing the Yucatan Peninsula, and the highlands of the Sierra Madre, running from the Mexican state of Chiapas, across southern Guatemala and onwards into El Salvador, and the southern lowlands of the Pacific littoral plain. The Archaic period, prior to 2000 BC, saw the first developments in agriculture and the earliest villages.
Investigation of Maya civilization
The agents of the Catholic Church wrote detailed accounts of the Maya, in support of their efforts at evangelization, and absorption of the Maya into the Spanish Empire. This was followed by various Spanish priests and colonial officials who left descriptions of ruins they visited in Yucatan and Central America. In 1839, American traveller and writer John Lloyd Stephens set out to visit a number of Maya sites with English architect and draftsman Frederick Catherwood. Their illustrated accounts of the ruins sparked strong popular interest, and brought the Maya to the attention of the world. The later 19th century saw the recording and recovery of ethnohistoric accounts of the Maya, and the first steps in deciphering Maya hieroglyphs.  The final two decades of the 19th century saw the birth of modern scientific archaeology in the Maya region, with the meticulous work of Alfred Maudslay and Teoberto Maler. By the early 20th century, the Peabody Museum was sponsoring excavations at Copan and in the Yucatan Peninsula. In the first two decades of the 20th century, advances were made in deciphering the Maya calendar, and identifying deities, dates, and religious concepts. Since the 1930s, archaeological exploration increased dramatically, with large-scale excavations across the Maya region.  In the 1960s, the distinguished Mayanist J. Eric S. Thompson promoted the ideas that Maya cities were essentially vacant ceremonial centres serving a dispersed population in the forest, and that the Maya civilization was governed by peaceful astronomer-priests. These ideas began to collapse with major advances in the decipherment of the script in the late 20th century, pioneered by Heinrich Berlin, Tatiana Proskouriakoff, and Yuri Knorozov. With breakthroughs in understanding of Maya script since the 1950s, the texts revealed the warlike activities of the Classic Maya kings, and the view of the Maya as peaceful could no longer be supported.

Q: Why was the Maya civilization being investigated?
A: The agents of the Catholic Church wrote detailed accounts of the Maya, in support of their efforts at evangelization, and absorption of the Maya into the Spanish Empire.
Was there anything bad that caused the investigation as well?
Their illustrated accounts of the ruins sparked strong popular interest, and brought the Maya to the attention of the world.
Their illustrated accounts of the ruins sparked strong popular interest, and brought the Maya to the attention of the world.