During which decade did horse-drawn steam engines begin to become obsolete?

The correct answer indicates that horse-drawn steam engines began to become obsolete in the 1920s due to significant advancements in technology and transportation during that period. This decade saw the widespread adoption of gasoline-powered vehicles, which offered greater efficiency and speed compared to horse-drawn steam engines. As automobiles and trucks replaced older transportation methods, the reliance on steam engines drawn by horses diminished rapidly. Innovations in manufacturing and increased availability of affordable vehicles contributed to this transition, making the 1920s a pivotal time as society moved towards modern transportation solutions. The shift marked a significant change in how goods and people were transported, signaling the end of an era where horse-drawn steam engines were once prevalent.