Well, here's my ESTC bit.  Not terribly exciting, I'm afraid.  My thinking
was that comparing the number of publications printed in a given city would
be pretty accurate criteria in determining what was considered the "center"
of commerce/academia/politics during colonial times.  So, I followed three
cities in ten year intervals from 1700 to 1790.  Surprise, surprise, over
time, Philadelphia replaces Boston as the place to be published in 18th
century America.
<pre>
FIND IPL BOSTON AND IYR 170# - 412 records 
FIND IPL NEW YORK AND IYR 170# - 104 records
FIND IPL PHILADELPHIA AND IYR 170# - 26 records

FIND IPL BOSTON AND IYR 171# - 633 records  
FIND IPL NEW YORK AND IYR 171# - 94 records  
FIND IPL PHILADELPHIA AND IYR 171# - 35 records  

FIND IPL BOSTON AND IYR 172# - 804 records
FIND IPL NEW YORK AND IYR 172# - 114 records 
FIND IPL PHILADELPHIA AND IYR 172# - 169 records  

FIND IPL BOSTON AND IYR 173# - 619 records
FIND IPL NEW YORK AND IYR 173# - 175 records
FIND IPL PHILADELPHIA AND IYR 173# - 159 records

FIND IPL BOSTON AND IYR 174# - 940 records
FIND IPL NEW YORK AND IYR 174# - 136 records
FIND IPL PHILADELPHIA AND IYR 174# - 424 records

FIND IPL BOSTON AND IYR 175# - 890 records 
FIND IPL NEW YORK AND IYR 175# - 245 records
FIND IPL PHILADELPHIA AND IYR 175# - 402 records

FIND IPL BOSTON AND IYR 176# - 1045 records
FIND IPL NEW YORK AND IYR 176# - 420 records 
FIND IPL PHILADELPHIA AND IYR 176# - 727 records

FIND IPL BOSTON AND IYR 177# - 1311 records 
FIND IPL NEW YORK AND IYR 177# - 773 records
FIND IPL PHILADELPHIA AND IYR 177# - 1488 records

FIND IPL BOSTON AND IYR 178# - 951 records
FIND IPL NEW YORK AND IYR 178# - 654 records
FIND IPL PHILADELPHIA AND IYR 178# - 1592 records

FIND IPL BOSTON AND IYR 179# - 2106 records 
FIND IPL NEW YORK AND IYR 179# - 1402 records
FIND IPL PHILADELPHIA AND IYR 179# - 4264 records
</pre>