Short answers, pulled from the story.
The small Ubaid settlement named Unug merged with its neighbor Kullaba to form Uruk in the mid-4th millennium BC. This new city grew from scattered agricultural villages into a massive urban center covering 600 hectares by the Late Uruk period.
Around 190 clay tablets dated to the Uruk V period c. 3500 BC contained numerical or impressed symbols while another 1776 tablets emerged from the Uruk IV period c. 3300 BC. One tablet mentioned Kushim who recorded transactions involving 29,086 measures of barley over 37 months which appears to be the oldest known writing featuring a person's identity.
Gilgamesh ruled Uruk in the 27th century BC according to this chronology and built the walls of Uruk while being described as victorious over Aga. Meshkiangasher held titles of both Lord and King of Eanna while claiming kingship over all of Sumer and Enmerkar supposedly reigned for at least 50 years and invented writing in legend.
William Loftus visited the site of Uruk in 1849 identifying it as Erech known as the second city of Nimrod and led excavations from 1850 to 1854 after a scouting mission. In total archaeologists spent 39 seasons working at Uruk with recent work from 2001 to 2002 including magnetometer surveys conducted by Margarete van Ess with Joerg Fassbinder and Helmut Becker.
The Mask of Warka dates from 3100 BC and is one of the earliest representations of the human face which stands approximately 20 centimeters tall and may depict the goddess Inanna. It was looted from the Iraq Museum during the invasion of Iraq in April 2003 before being recovered in September 2003.