Long-term mortgage loans are financial agreements where a borrower takes out a loan to purchase real estate, typically with a repayment period ranging from 15 to 30 years. These loans became increasingly popular in the 1920s as more Americans sought home ownership, contributing to a housing boom and economic expansion. The structure of these loans allowed for lower monthly payments, making it easier for families to invest in property and fostering a culture of consumerism and credit reliance.