Why did the pace of american overseas economic expansion quicken after the panic of 1873? apush?

This happened in the time of the Second Great Industrial Revolution which started right at that time, at near the end of the 19 century. There was a first truly national market as the country was connected through railroads. The second big thing was that the industries started merging thus creating monopolies. There were fever companies but they became more popular and their expansion helped them increase profits.