user1878: What are the authoritative sources for historic Bitcoin prices? 
Ideally this will be an API for all major exchanges.

user1878: At the bottom of that linked google docs spreadsheet are instructions to download data from Mt Gox and many other Exchanges. Namely:

Go to this link: http://bitcoincharts.com/charts/mtgoxUSD#tgSzm1g10zm2g25zv
Click load raw data

This raw data only maintains daily prices.  This is probably the closing price for the day, but I can't be sure of that.
I'm not sure how bitcoin charts actually collects this information from the other providers.  I hope other 

user54259: Many API endpoints included OHLC data from various exchanges can be found on

cryptowatch
cryptocompare


user108: All historical data from any exchange available at Bitcoin Charts: Markets API

Historic Trade Data
Trade data is available as CSV, delayed by approx. 15 minutes. It will return the 2000 most recent trades.
  Format:
https://api.bitcoincharts.com/v1/trades.csv?symbol=SYMBOL[&start=UNIXTIME]
Returns CSV with columns: unixtime,price,amount 
Example
Latest Kraken EUR trades:
  https://api.bitcoincharts.com/v1/trades.csv?symbol=krakenEUR


1878: <p>What are the authoritative sources for historic Bitcoin prices? </p>

<p>Ideally this will be an API for all major exchanges.</p>
 1878: <p>At the bottom of that linked google docs spreadsheet are instructions to download data from Mt Gox and many other Exchanges. Namely:</p>

<ul>
<li><p>Go to this link: <a href="http://bitcoincharts.com/charts/mtgoxUSD#tgSzm1g10zm2g25zv" rel="nofollow">http://bitcoincharts.com/charts/mtgoxUSD#tgSzm1g10zm2g25zv</a></p></li>
<li><p>Click load raw data</p></li>
</ul>

<p>This raw data only maintains daily prices.  This is probably the closing price for the day, but I can't be sure of that.</p>

<p>I'm not sure how bitcoin charts actually collects this information from the other providers.  I hope other </p>
 54259: <p>Many API endpoints included OHLC data from various exchanges can be found on</p>

<ul>
<li><a href="https://cryptowat.ch/docs/api" rel="nofollow noreferrer">cryptowatch</a></li>
<li><a href="https://www.cryptocompare.com/api/#introduction" rel="nofollow noreferrer">cryptocompare</a></li>
</ul>
 108: <p>All historical data from any exchange available at <a href="https://bitcoincharts.com/about/markets-api/" rel="nofollow noreferrer">Bitcoin Charts: Markets API</a></p>

<blockquote>
  <p><strong>Historic Trade Data</strong></p>
  
  <p>Trade data is available as CSV, delayed by approx. 15 minutes. It will return the 2000 most recent trades.
  Format:</p>
  
  <p><code>https://api.bitcoincharts.com/v1/trades.csv?symbol=SYMBOL[&amp;start=UNIXTIME]</code></p>
  
  <p>Returns CSV with columns: <code>unixtime,price,amount</code> </p>
  
  <p><strong>Example</strong></p>
  
  <p>Latest <em>Kraken EUR</em> trades:
  <a href="https://api.bitcoincharts.com/v1/trades.csv?symbol=krakenEUR" rel="nofollow noreferrer">https://api.bitcoincharts.com/v1/trades.csv?symbol=krakenEUR</a></p>
</blockquote>
