U.S. national debt surpassed $40 trillion, according to recent figures, prompting concerns about fiscal sustainability and potential economic impact. The debt took nearly 200 years to reach the $1 trillion mark in 1981, a milestone that was described as a wake‑up call at the time. Since 2016, when the debt stood just under $20 trillion, it has roughly doubled, reaching more than $40 trillion. Interest payments on the debt have risen 15% from the previous year and now represent about 20% of federal tax revenue, exceeding defense spending. The increase is driven by higher spending on social programs and pandemic‑related aid, combined with tax cuts that have reduced revenue. Long‑term interest rates are at multi‑decade highs, partly because of inflation concerns and large government borrowing. The bond market has demanded higher yields as investors allocate cash to both Treasury securities and to technology firms borrowing heavily for artificial‑intelligence investments. Economists note that rising rates make financing the deficit more costly, and that weakening investor appetite for U.S. debt could create a feedback loop requiring ever higher returns to attract purchasers. Households may face higher rates on mortgages, auto loans and credit cards, which could disproportionately affect lower‑income consumers, while higher borrowing costs for businesses may be passed on to consumers in the form of higher prices. The debt ceiling is near $41.1 trillion, and the Congressional Budget Office projects the debt could reach about $64 trillion by 2036. Economists say the United States still has a longer fiscal runway because of its reserve‑currency status, but they warn that without sustained economic growth or policy changes such as tax reforms or spending reductions, the debt burden could become more challenging to manage.