Karl Johansslussen

The two gates are sheeted with steel and lowered from the overhead road bridge, each of them operated with individual machinery hidden in the premises south of the canal.

Ships, still pulled by hand over the shallow passage, couldn't pass at all during some seasons and regularly ran ashore causing constant and expensive repairs, while the sheds and simple buildings next to it were often washed away by floods in spring and autumn.

In spite of the constant need of repair, the canal and its lock was an instant success, the city's earnings from customs increased sixfold, and as the loading an unloading of iron was relocated to the old moat in 1662, the area developed into one of the most vital ports in Europe, after 1636 handling approximately two-thirds of the Swedish export.

[5] Following the death of Charles XII in 1718, and the defeat in the Great Northern War (1700–1721) the Swedish capital was a city in despair, preparing for a Russian attack and encamped by impoverished, refugees, and idle soldiers.

The southern lock of the city was approaching a century in age, a bottleneck in a state of decay, inadequate for both the larger shipping vessels of the era and the increasing traffic load.

While Göran Josuæ Adelcrantz (1668–1739), the pupil and successor of Tessin the Younger, was mostly occupied by the construction works of the new Royal Palace, in 1622 he accomplished an emergency repair of the old lock; workers wading between the temporary embankments filling cracks with clay, straw, and muck, while loose and missing planks were put back in place.

These measure not only ended much more expensive than intended but also proved completely insufficient, and as the decay had obviously made the old lock impossible to repair properly, Christopher Polhem (1661–1751), "the father of Swedish mechanics", was consulted for a new construction.

The proposal of Adelcrantz for a new construction, estimated to cost 32,741 riksdaler in silver coins, was passed over by a suggested repair of the old lock by Johan Eberhard Carlberg (1683–1773) in 1726, limited in cost to 30,000 rikdaler while implying widening the canal from 6,5 to 8,2 meters, a proposal to the taste of the city's building board which subsequently had Adelcrantz replaced by Carlberg.

Half a dozen metal pump stocks 12 inches (300 mm) in diameter were found in the embankment but not understood as such, the entire machinery therefore thrown out of gear, while skippers exceeding the permissible draught attempted to pull their ships over the sill.

Successive plans for a new bridge were first encouraged as His Majesty personally granted subsidies worth 20,000 riksdaler annually during a period of ten years starting from 1837, provided that the city allocated the same amount to cover the cost was estimated to 394,000 riksdaler, the plans then fell upon problems however, as a competition in 1841 awarding the winning proposal 200 ducats produced no entries, and a new competition in 1843 awarding 500 ducats resulted in the same outcome.

The savior appeared in 1845 when lieutenant colonel Nils Ericson (1802–1870), who had worked for Baltzar von Platen at Göta Canal, delivered a proposal for which was, except for the award, also given 2,000 riksdaler for a supplemental investigation.

He concluded there were insufficient stonemasons in the Stockholm area, and therefore had limestone and granite brought in from other parts of Sweden, quarries Ericson knew well from his earlier projects.

He constructed a circular saw turned inwards to cut the head each stock at equal level for the bottom of the caisson, an instrument which was, like virtually all heavy tasks during the project, hand operated by several men.

Ericson gave directions for all sorts of tasks, including dredging, securing the rabbeting of planks, earth fillings, and determining the inclination of the caisson walls in order for them to withstand the pressure from the levees.

"[6] On the site, construction started in October 1846, with demolition of the old slaughterhouse, water mills, bazaars and an entire block, and temporary bridges were built on either sides of the old canal, while old curbs and piles were removed from the seabed.

A paved space was added south of the lock, Karl Johans Torg, and the sculptor Bengt Erland Fogelberg (1786–1854) created an equestrian statue of Charles XIV John (1763–1844), carried out in Rome and cast in Munich in 1852.

Its dimensions soon proved insufficient and a shipyard located upstream had to build its ships in two pieces, tow them through the lock to assemble them in a second yard downstream.