Final answer:
The demand for national magazines in the late 1800s was driven by increased education, advances in printing technology, and improved mail delivery infrastructure.
Step-by-step explanation:
The factors that contributed to the demand for national magazines in the late 1800s were indeed quite broad and interconnected. These factors included increases in public education, which expanded literacy and fostered a more informed citizenry eager for reading material. Advances in printing technologies, such as the invention of the linotype machine and the use of wood pulp for paper which significantly reduced costs and simplified the printing process, made printing faster and more economical, facilitating the mass production of magazines. Moreover, there were substantial improvements in mail delivery, such as the expansion of railroads and the introduction of steamboats and canals, which made the distribution of magazines across the country more efficient and reliable. Combined, these elements created an environment ripe for the proliferation of national magazines.