 After the War of 1812 , the first Europeans in the area were French settlers loyal to the British Crown who moved north from Detroit . They successfully traded with the Three Fires Confederacy , which contributed to the growth of the area . After its foundation , Port Sarnia expanded throughout the 19th Century ; on 19 June 1856 , the residents passed the Act to Incorporate the Town of Sarnia and the name Port Sarnia was officially changed to Sarnia effective 1 January 1857 . The Act mentioned 1 @,@ 000 inhabitants in three wards . The wealth of adjoining stands of timber , the discovery of oil in nearby Oil Springs in 1858 by James Miller Williams , and the arrival of the Great Western Railway in 1858 and the Grand Trunk Railway in 1859 all stimulated Sarnia 's growth . The rail lines were later linked directly to the United States by the opening of the St. Clair Tunnel under the St. Clair River at Sarnia in 1890 , by the Grand Trunk Railway , which was the first railroad tunnel ever constructed under a river . The tunnel was an engineering marvel in its day , achieved through the development of original techniques for excavating in a compressed air environment . 
 After the War of 1812 , the first Europeans in the area <a href='uninflect' title='1'><mark>were</mark></a> French settlers loyal to the British Crown <a href='null_relcl' title='2'><mark>who</mark></a>moved north from Detroit . They successfully traded with the Three Fires Confederacy , which contributed to the growth of the area . After its foundation , Port Sarnia expanded throughout the 19th Century ; on 19 June 1856 , the residents passed the Act to Incorporate the Town of Sarnia and the name Port Sarnia was officially changed to Sarnia effective 1 January 1857 . The Act mentioned 1 @,@ 000 inhabitants in three wards . The wealth of adjoining stands of timber , the discovery of oil in nearby Oil Springs in 1858 by James Miller Williams , and the arrival of the Great Western Railway in 1858 and the Grand Trunk Railway in 1859 all stimulated Sarnia <a href='null_genetive' title='3'><mark>'s</mark></a>growth . The rail lines <a href='uninflect' title='4'><mark>were</mark></a> later linked directly to the United States by the opening of the St. Clair Tunnel under the St. Clair River at Sarnia in 1890 , by the Grand Trunk Railway , which was the first railroad tunnel ever constructed under a river . The tunnel was an engineering marvel in its day , achieved through the development of original techniques for excavating in a compressed air environment . 
After the War of 1812 , da first Europeans in the area was French settlers loyal to tdaBritish Crown moved north from Detroit . They successfully traded with the Three Fires Confederacy , which contributed to the growth of the area . After its foundation , Port Sarnia expanded throughout thda9th Century ; on 19 June 1856 , thedasidents passed the da to Incorporate the Town of Sarnia and the nda Port Sarnia was officially changed to Sarnia effective 1 January 1857 . The Act mentioned 1 @,@ 000 inhabitants in three wards . The wedah of adjoining stands of timber , the disdaery of oil in nearby Oil Springs in 1858 by James Miller Williams , and the arrival of the Great Western Railway in 1858 and the Grandarunk Railway in 1859 alll stimulated Sarnia  growth . The rail lines was later linked directly to the United States by the opening of the St. Clair Tunnel under the St. Clair River at Sarnia in 1890 , by the Grand Trunk Railway , which was the first railroad tunnel ever constructed under a river . The tunnel was an engineering marvel in its day , achieved thru the develdaent of original techniques fir excavating in a compressed air environment .