Cornelius Weygandt was born on December 13, 1871, in Germantown, Pennsylvania. He was the son of Cornelius Nolan Weygandt and Lucy Elmaker Thomas. His ancestry consisted of a long linage of German immigrants. His great-great-grandfather, also named Cornelius Weygandt, immigrated from Osthofen, Germany, to Germantown, Pennsylvania, in 1736. Moving into a German community made the transition easier and helped keep his family's German culture alive. Four generations later, Cornelius Weygandt led a life that was strongly influenced by his ancestry, an influence evident by his writing.

Weygandt authored over eighteen books in his life. His father was a prominent banker, and his mother was a school teacher. Weygandt proved to be enthusiastic and was motivated to become a scholar. He enrolled at the University of Pennsylvania at the age of fifteen. However, by his own admission, he didn't catch on to the entire meaning of higher education until his third year there. Weygandt seemed to possess a thirst for knowledge uncommon for a boy of his age; he quenched his thirst with a great number of books and volumes of history, as it pertained to his heritage. Throughout his childhood, Weygandt busied himself studying all manner of things about the world around him. He showed interest in many topics ranging from the local woodland creatures to the nursery rhymes of the local Pennsylvania Dutch.

In his autobiography, On the Edge of Evening, Weygandt reminisces about his childhood, since he was different from most of his peers. He recalls the other children running and playing while he was busy with his texts or learning Latin. Most of his childhood friends were actually adults. He spent his free time listening to stories from his Aunt Rachel or Lawrence Kelly, the family gardener, who taught Weygandt rhymes as they worked together.

Throughout his life, Weygandt displayed a great compassion for all creatures great and small. Although this was instilled in him at a young age, it remained with him through his life and is evident in his later writings. His writings are an example of a man whose passion for the findings of nature are driven by a rich imagination.

In his autobiography, Weygandt states, "My belief about writing is that one should be so lost in a subject that is possesses him and makes him forget everything but what he is writing about. I have never had much patience with self-expression as an end in writing, what I have written about is this, that, and the other thing that has possessed me since childhood." This is evident in his works, which are various non-fiction pieces reflecting a compilation of his life experiences.

The first book that Weygandt authored, Irish Plays and Playwrights, was written in 1913. During the period that he spent writing his first book, Weygandt also taught at The University of Pennsylvania full time. He labored on his writing during the night after he had reviewed his lecture notes for the next day.

Weygandt took few things more seriously than teaching. Although he planned out his lectures, he believed it was necessary to not directly read anything to his students, explaining that it would make the lectures more tedious for them. Instead, he memorized quotes and made sure he had a thorough understanding of the material so the message was clear and captivating. Understandably, it took him quite a while to finish the book because his other commitments.

In 1925, Weygandt wrote his second book, A Century of the English Novel. Weygandt produced this book much more quickly due to his familiarity with the subject, which he had spent the previous 25 years lecturing about. In On the Edge of Evening, Weygandt speaks of his first two books. He admits that his first book was given harsher reviews by literary critics but says that the claims he had made held true over time.

After his second book was published in 1925, Weygandt's writing took off. He found his niche and was able to produce his next book, Tuesdays at Ten, even more quickly. Weygandt wrote the book to target his former students. It consisted of multiple lectures and lessons that he had taught and copied down almost verbatim. It outlined the history of the state that he loved so much and the school that molded him. It was a hit with many of his former students, selling over 1,250 copies, and he personally signed about 250 of those copies.

Weygandt's next book was a personal testament of his heritage. The Red Hills outlines the Pennsylvania Dutch lifestyle as Weygandt had experienced it. It represents the first book in which Weygandt exposed his true passion for his heritage. He had been considering writing a book on the subject of Pennsylvania Dutch for nearly forty years and finally felt that he was ready to write it. Weygandt opposed the movement to correct the phrase to Pennsylvania German. He felt that most of the greatest things about the heritage would be forever tagged as Dutch. Dutch cookbooks, Dutch furniture, Dutch pretzels, and more would be lost to their rightful owners if they were called Pennsylvania German.

The Wissahickon Hills, published in 1930, was Weygandt's first book concentrating on his appreciation of nature. It focuses on Pennsylvania's native birds.

The next book that Weygandt wrote also shared the Pennsylvania outdoors theme. A Passing America reveled in the memories of the historic covered bridges and the log cabins of the turn of the century.

In The White Hills, Weygandt writes about New Hampshire. He describes the summers he spent at his parents' cabin in the White Mountains. The book has been considered New Hampshire's version of The Red Hills, which concentrated on all things Pennsylvania. There was an influx of visitors to the New Hampshire area following the release of the book. Many residents considered him a great interpreter of New Hampshire despite his deep roots in Pennsylvania.

Weygandt continued to concentrate his writing on New Hampshire for a few years, finding great comfort in the expanded repertoire that it gave him. Weygandt authored The Blue Hills. It is comparable to his previous work, The Red Hills, although he tried to broaden his focus from solely the Pennsylvania Dutch to all people living in Pennsylvania. He wrote about the British, the Quakers, and the Scotch-Irish in addition to the Pennsylvania Dutch.

Weygandt continued his writing and teaching into old age. His last published work was his autobiography called On the Edge of Evening. The title suggests that he knew he was going to die soon. He died in 1957. His life was rich with the things that he held dearest. He was loved by his family, respected by his colleagues and students, and admired by his readers.