After the death of his father, Stieglitz inherited the banking-house and succeeded as a banker of the Emperor. In 1840–1850, he successfully sold six 4% government loans to finance the construction of the Moscow – Saint Petersburg Railway and secured a significant foreign loan at the height of the Crimean War. Stieglitz also owned manufacturing enterprises in Narva and in Catherinehof.
In 1846, Stieglitz was elected the chairman of the Exchange's committee. At that post, he took part in all financial operation of the Government of the Russian Empire. In 1857, he co-founded the Society of the Russian Railways. In 1860, Stieglitz liquidated all his commercial enterprises and voluntarily withdrew from the post of the chairman of the Exchange's committee.
On 31 May 1860, Emperor Alexander II established the State Bank of the Russian Empire and Stieglitz became its first governor. In 1866, he left the state service.