The Pearl Knoop papers date from 1933 to 1998 and measure 3.25 linear feet. The papers are a record of Knoop's bird watching activities during these years; they also contain weather data from newspaper clippings and a card file of her bird sightings. The daily bird watching diaries provide some insight into Knoop's daily life, noting where she was and what she was doing when she sighted particular birds. On April 28, 1937, for example, she wrote, "Came back from Floyd again Monday evening as school closed on account of Scarlet Fever. Went over to Schwartz' this afternoon, saw two Shrikes on way over... Clair saw a Franklin Gull today."

Records from 1933-1940 and 1996-1998 are less complete than records from other periods. The 1967 list contains an article written by Knoop on her bird watching activities for the Charles City Press.  In "Iowa Birds: Aunt Pearl's List," Knoop wrote about how she became interested in bird watching. "We liked our Baltimore Orioles," she writes. "Now the AOU [American Ornithologist Union] has changed their names to Northern Orioles. I didn't approve."