Early in 1841 the project of widening and deepening the Welland Canal began to be discussed with some vehemence in Upper Canada. With a view to securing a contract, Mr. Gzowski came over from Erie, Pennsylvania (where he then resided), to Toronto, and for the first time was brought into contact with some of the leading public men of Canada. The Government was then administered by Sir Charles Bagot, a gentleman whose infirm state of health did not prevent him from taking a warm interest in the public improvements of the country. Sir Charles formed a high opinion of Mr. Gzowski's talents, and sanctioned his appointment to an office in connection with the Department of Public Works. This appointment having been accepted by Mr. Gzowski, he bade adieu to his many friends in the United States, and took up his abode in Upper Canada.
During the next six years Mr. Gzowski's life was entirely occupied by his duties in connection with the Department of Public Works. It is manifestly out of the question to give even an epitome of the numberless important enterprises conducted by him during this, the busiest period of his active life. His reports of the works in connection with harbours, bridges and highways alone occupy a considerable portion of a large folio volume. It will be sufficient to say that every important provincial improvement came under his supervision, and that nearly every county in Upper Canada bears upon its surface the impress of his great industry and engineering skill. In 1846 he obtained naturalization and became a British subject. Soon after the accession to power of the Baldwin-Lafontaine Government, in 1848, his services in an official capacity were brought to a close, and he began to enter upon large engineering enterprises on his own account. Towards the end of the year 1848 he published a report on the mines of the Upper Canada Mining Company on Lake Huron. But his mind was occupied by more important schemes. The railway era set in. The Railroad Guarantee Act, authorizing Government grants to private companies undertaking the construction of railways, having been passed in 1849, the public began to hear of various railway projects of greater or lesser importance. The first great enterprise of this sort with which Mr. Gzowski connected himself was the St. Lawrence and Atlantic Railroad Company, from Montreal to Island Pond, which has since been amalgamated with the Grand Trunk. Mr. Gzowski was appointed Chief Engineer of this undertaking, made a survey of the greater portion of the line, and superintended the actual construction. When the line became merged in the Grand Trunk he resigned his position of Chief Engineer, and received the most gratifying written testimonials from the Board of Directors as to his able administration of the important duties which had fallen to his share. Having formed a partnership with the present Sir Alexander T. Galt, the late Hon. Luther H. Holton, and the Hon. D. L. Macpherson, Mr. Gzowski for some years devoted himself entirely to the work of railway construction. On the 24th of March, 1853, the firm of Gzowski & Co. obtained the contract for the construction of the line from Toronto westward to Sarnia. This great work was prosecuted to a successful conclusion, and was attended with most gratifying pecuniary results to the contractors. The firm was then dissolved, and has since consisted of Messrs. Gzowski and Macpherson only, who continued to carry on large operations in the way of railway construction. Among other railway works constructed by the firm were the line from Port Huron to Detroit, in the State of Michigan, and the line from London to St. Mary's, in this Province. In connection with their own enterprises, and for the purpose of supplying railway companies with iron rails and materials used in the construction of railways, Messrs. Gzowski & Macpherson in 1857 established the Toronto Rolling Mills, which were carried on successfully for about twelve years. Steel rails having largely superseded the use of iron ones, the necessity for maintaining the establishment ceased to exist, and the works were closed up in 1869.