When he was nine years old his father removed to Louisville, Kentucky.  During the voyage down the Ohio, young Eads passed the most of his time in watching the engines of the steamer.  The engineer was so much pleased to see his interest in the machinery that he explained the whole system of the steam-engine to him.  The boy listened eagerly, and every word remained fixed in his mind.  Two years later, with no further instruction on the subject, he constructed a miniature engine, which was worked by steam.  This, for a boy of eleven years, was no insignificant triumph of genius.  His father, anxious to encourage such unmistakable talent, now fitted up a small workshop for him, in which he constructed models of saw mills, fire engines, steamboats, and electrotyping machines.  When he was only twelve years old he was able to take to pieces and reset the family clock and a patent lever watch, using no tool for this purpose but his pocket-knife.

At the age of thirteen his pleasant employment was brought to a sudden end.  His father lost all his property by the failure of some commercial transactions, and the family was brought to the verge of ruin.  It now became necessary for young Eads to labor for his own support, and for that of his mother and sisters.  Boy as he was, he faced the crisis bravely.  Having in vain sought employment in Louisville, he resolved to go to St. Louis.  He worked his passage there on a river steamer, and landed in that city so poor that he had neither shoes to his feet nor a coat to his back.  He found it as difficult to procure work here as it had been in Louisville, and was at length compelled to resort to peddling apples on the street in order to secure a living.  He did this for some time, never relaxing his efforts to obtain more desirable employment.

After many attempts he succeeded in getting a situation in a mercantile house, at a fair salary.  One of his employers was a man of wealth and culture, and was possessed of one of the finest private libraries in the West.  Learning the extraordinary mechanical talent possessed by his young clerk, this gentleman placed his library at his disposal.  The offer was promptly and gratefully accepted, and young Eads devoted almost all his leisure time to the study of mechanics, machinery, and civil engineering.  He remained with this house for several years, and then obtained a clerkship on one of the Mississippi River steamers, where he passed several years more.  During this time he became intimately acquainted with the great river and its tributaries, and acquired an extensive knowledge of all subjects appertaining to western navigation, which proved of great service to him in his after life.