Written by Idontknow
The puzzle consists of two columns of cities and a scattered arrangement of rivers in the center. Note that the right column of cities is alphabetized, which suggests its ordering isn't important.
Each river in the middle connects one city on the left and one city on the right, and if you draw a line between the cities' dots, it intersects exactly one letter of their connecting river:
|Left city||River||Right city||Extracted letter|
|St. Louis||Mississippi||New Orleans||S|
|Albuquerque||Rio Grande||Ciudad Juárez||E|
The extracted letters in the provided order of the left-hand cities can be fit into the blanks to produce the final cluephrase, ST WHAT SEAWAY. Googling this produces many results for the St. Lawrence Seaway, a system of canals connecting the Great Lakes to the Atlantic Ocean. The answer is LAWRENCE.