The Great Pilgrimage was the largest march organized by the NUWSS. Taking place over several weeks in the Summer of 1913, the march was the culmination of the NUWSS efforts at organized marches and rallies. Over 50,000 women from across England and Wales marched across the countryside to London. Once they arrived, they gathered in Hyde Park for a rally. The march took weeks to finish, and was covered extensively by the press. The march was praised for its polished execution and lack of violence, and garnered extensive public sympathy. While there was negative press, the event was covered more favorably than might have been expected.
The first source is an overview of women's marches, with a particular focus on The Great Pilgrimage and the Mud March. The second is an overview of the day, which includes several useful scanned documents, and a full list of societies and personnel.
“Women's Suffrage Procession through Cambridge of Sat 19th July 1913.” Lost Cambridge, 1 Dec. 2017, lostcambridge.wordpress.com/2017/12/01/womens-suffrage-procession-through-cambridge-of-sat-19th-july-1913/.