In the course of the following year the organization of the Baltimore and
Ohio Railroad, a part of which had already been constructed under the
immediate personal supervision of Lieutenant Whistler, assumed a more
permanent form, and allowed the military engineers to be transferred to
other undertakings of a similar character. Accordingly, in June, 1830,
Captain McNeill and Lieutenant Whistler were sent to the Baltimore and
Susquehanna Railroad, for which they made the preliminary surveys and a
definite location, and upon which they remained until about twenty miles
were completed, when a lack of funds caused a temporary suspension of the
work. In the latter part of 1831 Whistler went to New Jersey to aid in the
construction of the Paterson and Hudson River Railroad (now a part of the
Erie Railway). Upon this work he remained until 1833, at which time he
moved to Connecticut to take charge of the location of the railroad from
Providence to Stonington, a line which had been proposed as an extension of
that already in process of construction from Boston to Providence.

In this year, December 31, 1833, Lieut. Whistler resigned his commission in
the army, and this not so much from choice as from a sense of duty.
Hitherto his work as an engineer appears to have been more an employment
than a vocation. He carried on his undertakings diligently, as it was his
nature to do, but without much anxiety or enthusiasm; and he was satisfied
in meeting difficulties as they came up, with a sufficient solution.
Henceforward he handled his profession from a love of it. He labored that
his resources against the difficulties of matter and space should be
overabundant, and if he had before been content with the sure-footed facts
of observation, he now added the luminous aid of study. How luminous and
how sure these combined became, his later works show best.

In 1834 Mr. Whistler accepted the position of engineer to the proprietors
of locks and canals at Lowell. This position gave him among other things