Final answer:
In 1840, the United States had approximately C.1,000 weekly newspapers, a reflection of the thriving newspaper industry due to technological advances and the penny press.
Step-by-step explanation:
The number of weekly newspapers that the United States had in 1840 was approximately 1,000. This period marked a significant growth in the newspaper industry, facilitated by advancements such as the linotype machine, which made production faster and less expensive. Additionally, the expansion of roads and waterways reduced the costs of distributing printed materials. Notably, the penny press catered to a broader audience with affordable prices. By 1841, journalistic standards began to rise with newspapers like the New-York Tribune under Horace Greeley becoming nationally respected publications.