Between 1890–1900 the rate of new railroad construction had dropped significantly from the peak of the early 1880s. The trend of network growth into the western states continued as their coverage began to catch up with the states of the east coast. The introduction of two major safety innovations, the knuckle coupler and the air brake, which were required to be fitted on all rail cars under federal law in 1893, further increased the safety conditions for rail workers and allowed locomotives to be brought to a stop much more efficiently. Additionally, railroads across the country began the upgrade to steel rails, which were much more durable than the iron rails that had previously been used. The economic depression that hit America in 1893 took its toll on the railroad industry, forcing well established companies such as the Union Pacific Railway and Baltimore and Ohio Railroad to declare bankruptcy.