"The first major series of publications [John] Marshall instituted in the very beginning of his career [as Director-General of the Archaeological Survey of India, ASI] was the Annual Reports, published first in 1902-3 under the title Archaeological Survey of India: Annual Report 1902-3 (Calcutta, 1904)" writes Dilip K. Chakrabarti in his book A History of Indian Archaeology (p. 127).
In these reports, often but not always published the same year or shortly thereafter, archaeologists like Daya Ram Sahni, who had excavated at Harappa, offered the first descriptions and notes of what was just found at the site.
Fortunately, the ASI has made these volumes like the entire Annual 1921 ASI Report available on Archive.org. Below is an abridged copy that presents only the sections and images relevant to that year's excavations at Harappa.
Download the Annual Progress Report 1921's relevant Harappa pages as a PDF.