19th and 20th centuries to store and ship the area's grains and produce. Brick commercial buildings are spread throughout downtown. Once the site of several brick factories, Alton has an unusually high number of streets still paved in brick. The lower levels of Alton are subject to floods, many of which have inundated the historic downtown area. The dates of different flood levels are marked on the large grain silos, part of the Ardent Mills, near the Argosy Casino at the waterfront. The flood of 1993 is considered the worst of the last century. Alton became an important town for abolitionists, as Illinois was a free state across from the slave state of Missouri. Pro-slavery activists also lived there and slave catchers often raided the city. Escaped slaves would cross the Mississippi to seek shelter in Alton, and proceed to safer places through stations of the Underground Railroad. During the years before the American Civil War, several homes were equipped with tunnels and hiding places for stations on the Underground Railroad to aid slaves escaping to the North. On November 7, 1837, the abolitionist printer Reverend Elijah P. Lovejoy was murdered by a pro-slavery mob while he tried to protect his Alton-based press from being destroyed for the third time. He had moved from St. Louis because of opposition there. He had printed many abolitionist tracts and distributed them throughout the area. When one of the mob made a move to set the old warehouse on fire, Lovejoy, armed with only a pistol, went outside to try to stop him. The pro-slavery man shot him dead (with a shotgun, five rounds through the midsection). The mob stormed the warehouse and threw Lovejoy's printing press into the Mississippi. Lovejoy thus became the first martyr of the abolition movement. Alton became the seat of a diocese of the Catholic Church in 1857. Its first bishop was French-born Henry Damian Juncker. The new diocese had 58 churches, 18 priests and 50,000 Catholics. When he died, 11 years later, the churches were 125, the priests more than 100, and the Catholics 80,000. He was succeeded by Peter Joseph Baltes from Germany (1869–1886) and James Ryan (1888–1923). In 1923 the bishop's seat was moved to Springfield, Illinois. The Diocese of Alton, no longer a residential bishopric, is today listed by the Catholic Church as a titular see. Titular bishops appointed to the see have been