Historians have regularly assumed the transparency of census statistics on women's employment  in Chile, which suggest a steady decline in female employment -particulary  in industry- from the late nineteenth through the early twentieth century. Arguing that quantitative sources are like other historical documents social constructions, this article first explores the limitations of the Chilean census as an accurate measure of female economic activity. The article hen shows how, because the progressive "modernization" of the census implied substantive changes in the collection and interpretation of census data, women's economic activity became increasingly invisible as the century progressed. This critical reading of census materials allows us both to question contemporary assumptions about women's economic participation and to examine the changing notions of labor that were integral to the formation of state labor and welfare policies in early twentieth-century Chile.