Short answers, pulled from the story.
Frederick C. Leonard pondered the existence of a trans-Neptunian population shortly after Clyde Tombaugh discovered Pluto in 1930. He asked whether Pluto was merely the first of many ultra-Neptunian bodies destined for future detection.
Jewitt and Luu announced on the 30th of August 1992 the discovery of candidate Kuiper belt object 1992 QB1. This object was later named 15760 Albion.
The Kuiper belt stretches from roughly 30 to 55 AU including its outlying regions but excluding the scattered disc. The main body extends from the 2:3 mean-motion resonance at 39.5 AU to the 1:2 resonance at roughly 48 AU.
New Horizons launched the 19th of January 2006 flew by Pluto the 14th of July 2015. On the 1st of January 2019 successfully flew by Arrokoth returning data showing contact binary 32 km long by 16 km wide.
By 2018 over 2000 Kuiper belt objects had been discovered. Over one thousand bodies were found in a belt during the twenty years from 1992 to 2012 after finding 15760 Albion.